Internship report of NTPC kawas ,summer internship report of ntpc
LalitGoyal27
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Dec 17, 2018
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About This Presentation
National Thermal Power Plant Kawas Project report,summer internship report of ntpc ,internship report, national thermal power plant kawas project report, summer internship report of ntpc,ntpc summer training report,ntpc training repntpc training reportort
Slide Content
INDUSTRIAL TRAINING PROJECT REPORT
ON
“GAS BASED THERMAL POWER PLANT”
NATIONAL THERMAL POWER CORPORATION,
KAWAS SURAT (GUJARAT)
Duration:- 03/12/2018-17/12/2018
Submitted by: Submitted to:
Lalit I/C Training Department
Electrical Engineering National Thermal Power
SVNIT Corporation Limited
Surat (Gujarat) Kawas , Surat(Gujarat)
ON
“GAS BASED THERMAL POWER PLANT”
NATIONAL THERMAL POWER CORPORATION,
KAWAS SURAT (GUJARAT)
Duration:- 03/12/2018-17/12/2018
Submitted by: Submitted to:
Lalit I/C Training Department
Electrical Engineering National Thermal Power
SVNIT Corporation Limited
Surat (Gujarat) Kawas , Surat(Gujarat)
DECLARATION
I , Mr. Lalit , hereby declare that this project is being
submitted in fulfilment of the Industrial Training
Programme in NTPC Kawas Surat , and is result of
self done work carried out by me under the various
guidance of engineers and other officers.
I further declare that to my knowledge , the structure
and content of this projected are original and have not
been submitted before any purpose
Mr. Lalit
B. Tech. 3 rd year (5
TH
Sem.)
Electrical Engineering
SVNIT Surat
I , Mr. Lalit , hereby declare that this project is being
submitted in fulfilment of the Industrial Training
Programme in NTPC Kawas Surat , and is result of
self done work carried out by me under the various
guidance of engineers and other officers.
I further declare that to my knowledge , the structure
and content of this projected are original and have not
been submitted before any purpose
Mr. Lalit
B. Tech. 3 rd year (5
TH
Sem.)
Electrical Engineering
SVNIT Surat
ACKNOWLEDGEMENT
Industrial Training is an integral part of engineering
curriculum providing engineers with first hand and practical
aspects of their studies. It gives them the knowledge about
the work and circumstances existing in the company. The
preparation of this report would not have been possible
without the valuable contribution of the NTPC family
comprising of several experienced engineers in their
respective field of work. It gives me great pleasure in
completing my training at Thermal power Plant of NTPC at
Kawas and submitting the training report for the same.
I take privilege to express my sincere thanks to Mr. Vivek Jha
, AGM (Electrical / C&I ) who supported us constantly and
channelize our work toward more positive manner.
I express my deepest gratitude to Mr. Sharad A Shinde Ass.
Manager (PR) for giving me the permission for orientation
in operational area of plant.
I am thankful to our mentor Mr. R.G. Patel who teaches every
minute detail of plant and practical Knowledge i.e. Without your
efforts the present form of this report is not possible.
In addition ,I am thankful to Mr. Mansukh Bhai who guided us
regarding safety factors & Major issue of NTPC plant.
Industrial Training is an integral part of engineering
curriculum providing engineers with first hand and practical
aspects of their studies. It gives them the knowledge about
the work and circumstances existing in the company. The
preparation of this report would not have been possible
without the valuable contribution of the NTPC family
comprising of several experienced engineers in their
respective field of work. It gives me great pleasure in
completing my training at Thermal power Plant of NTPC at
Kawas and submitting the training report for the same.
I take privilege to express my sincere thanks to Mr. Vivek Jha
, AGM (Electrical / C&I ) who supported us constantly and
channelize our work toward more positive manner.
I express my deepest gratitude to Mr. Sharad A Shinde Ass.
Manager (PR) for giving me the permission for orientation
in operational area of plant.
I am thankful to our mentor Mr. R.G. Patel who teaches every
minute detail of plant and practical Knowledge i.e. Without your
efforts the present form of this report is not possible.
In addition ,I am thankful to Mr. Mansukh Bhai who guided us
regarding safety factors & Major issue of NTPC plant.
CERTIFICATE
This is to certify that Mr. Lalit , bachelor of
Technology in Semester 5
TH
of Electrical Engineering
Department Sardar Vallabhbhai National Institute
of Technology , Surat has successfully completed
vocation training for a period of 15 days from
03.12.18 to 17.12.18 at National Thermal Power
plant kawas, Surat and has made the Training project
report under my guidance.
During this tenure, we found him to be sincere and hard
working ,we take this opportunity to wish him all the
very best in Future endeavours.
Training In-charge
Mr.Vivek Jha
Additional General Manager
(Electrical / C & I)
NTPC Kawas , Surat
This is to certify that Mr. Lalit , bachelor of
Technology in Semester 5
TH
of Electrical Engineering
Department Sardar Vallabhbhai National Institute
of Technology , Surat has successfully completed
vocation training for a period of 15 days from
03.12.18 to 17.12.18 at National Thermal Power
plant kawas, Surat and has made the Training project
report under my guidance.
During this tenure, we found him to be sincere and hard
working ,we take this opportunity to wish him all the
very best in Future endeavours.
Training In-charge
Mr.Vivek Jha
Additional General Manager
(Electrical / C & I)
NTPC Kawas , Surat
CONTENT:-
1. POWER GENERATION IN INDIA
1) ELECTRICAL DISTRIBBUTION
2) ELECTRICAL TRANSMISSION
2. OVERVIEW OF NTPC IN INDIA
3. OVERVIEW OF NTPC PLANT KAWAS
4. SALIENT FEATURES OF PLANT
5. COMBINE CYCLE POWER PLANT
6. INTRODUCTION GAS POWER STATION
7. STEAM TURBINE
8. GAS TURBINE
9. GENERATOR
1) STATOR
2) ROTOR
10. BOILERS
11. WATER SYSTEM
12. COOLING TOWER
13. SWITCHYARD
14. CONTROL SYSTEM AND RELAYS
15. SWITCHGEAR
16. TRANSFORMER
17. GENERATED POWER TRANSFER TO GRID
18. CONCLUSION
1. POWER GENERATION IN INDIA
1) ELECTRICAL DISTRIBBUTION
2) ELECTRICAL TRANSMISSION
2. OVERVIEW OF NTPC IN INDIA
3. OVERVIEW OF NTPC PLANT KAWAS
4. SALIENT FEATURES OF PLANT
5. COMBINE CYCLE POWER PLANT
6. INTRODUCTION GAS POWER STATION
7. STEAM TURBINE
8. GAS TURBINE
9. GENERATOR
1) STATOR
2) ROTOR
10. BOILERS
11. WATER SYSTEM
12. COOLING TOWER
13. SWITCHYARD
14. CONTROL SYSTEM AND RELAYS
15. SWITCHGEAR
16. TRANSFORMER
17. GENERATED POWER TRANSFER TO GRID
18. CONCLUSION
Electrical Power Sector In India:-
The power sector in India is mainly governed by the Ministry of Power. There
are three major pillars of power sector these are Generation, Transmission, and
Distribution. As far as generation is concerned it is mainly divided into three
sectors these are 1) Central Sector, 2)State Sector, and 3)Private Sector.
Central Sector or Public Sector Undertakings (PSUs), constitute 29.78%
(108.41GW) of total installed capacity i.e, 346.05 GW (as on 31/10/2018) in
India. Major PSUs involved in the generation of electricity include NHPC Ltd.,
NTPC Ltd. ,, and Nuclear Power Corporation of India (NPCIL).
Several state-level sector or corporations are there which accounts for
about 41.10% of overall generation , such as Jharkhand State Electricity Board
(JSEB), Maharashtra State Electricity Board (MSEB), Kerala State Electricity
Board (KSEB), in Gujarat (MGVCL, PGVCL, DGVCL, UGVCL four
distribution Companies and one controlling body GUVNL, and one generation
company GSEC), are also involved in the generation and intra-state distribution
of electricity.
Other than PSUs and state level corporations, Private sector enterprises also
play a major role in generation, transmission and distribution, about 29.11% of
total installed capacity is generated by private sector.
The Power Grid Corporation of India is responsible for the inter-state
transmission of electricity and the development of national grid.
The utility electricity sector in India has one National Grid (power Grid) with an
installed capacity of 346.05 GW as on 31 October 2018. Renewable
power plants constituted 33.60% of total installed capacity. During the fiscal
year 2017-18, the gross electricity generated by utilities in India was
1,303.49 TWh and the total electricity generation (utilities and non utilities) in
the country was 1,486.5 TWh. The gross electricity consumption was 1,149
kWh per capita in the year 2017-18. India is the world's third largest
producer and third largest consumer of electricity. Electric energy
consumption in agriculture was recorded highest (17.89%) in 2015-16 among
all countries. The per capita electricity consumption is low compared to many
countries despite cheaper electricity tariff in India.
India has surplus power generation capacity but lacks adequate infrastructure
for supplying electricity to all needy people. In order to address the lack of
adequate electricity supply to all the people in the country by March 2019,
the Government of India launched a scheme called "Power for All".
The power sector in India is mainly governed by the Ministry of Power. There
are three major pillars of power sector these are Generation, Transmission, and
Distribution. As far as generation is concerned it is mainly divided into three
sectors these are 1) Central Sector, 2)State Sector, and 3)Private Sector.
Central Sector or Public Sector Undertakings (PSUs), constitute 29.78%
(108.41GW) of total installed capacity i.e, 346.05 GW (as on 31/10/2018) in
India. Major PSUs involved in the generation of electricity include NHPC Ltd.,
NTPC Ltd. ,, and Nuclear Power Corporation of India (NPCIL).
Several state-level sector or corporations are there which accounts for
about 41.10% of overall generation , such as Jharkhand State Electricity Board
(JSEB), Maharashtra State Electricity Board (MSEB), Kerala State Electricity
Board (KSEB), in Gujarat (MGVCL, PGVCL, DGVCL, UGVCL four
distribution Companies and one controlling body GUVNL, and one generation
company GSEC), are also involved in the generation and intra-state distribution
of electricity.
Other than PSUs and state level corporations, Private sector enterprises also
play a major role in generation, transmission and distribution, about 29.11% of
total installed capacity is generated by private sector.
The Power Grid Corporation of India is responsible for the inter-state
transmission of electricity and the development of national grid.
The utility electricity sector in India has one National Grid (power Grid) with an
installed capacity of 346.05 GW as on 31 October 2018. Renewable
power plants constituted 33.60% of total installed capacity. During the fiscal
year 2017-18, the gross electricity generated by utilities in India was
1,303.49 TWh and the total electricity generation (utilities and non utilities) in
the country was 1,486.5 TWh. The gross electricity consumption was 1,149
kWh per capita in the year 2017-18. India is the world's third largest
producer and third largest consumer of electricity. Electric energy
consumption in agriculture was recorded highest (17.89%) in 2015-16 among
all countries. The per capita electricity consumption is low compared to many
countries despite cheaper electricity tariff in India.
India has surplus power generation capacity but lacks adequate infrastructure
for supplying electricity to all needy people. In order to address the lack of
adequate electricity supply to all the people in the country by March 2019,
the Government of India launched a scheme called "Power for All".
This scheme will ensure continuous and uninterrupted electricity supply to all
households, industries and commercial establishments by creating and
improving necessary infrastructure. It is a joint collaboration of the Government
of India with states to share funding and create overall economic growth.
India's electricity sector is dominated by fossil fuels, and in particular coal,
which in 2017-18 produced about three fourths of all electricity. However, the
government is pushing for an increased investment in renewable energy. The
National Electricity Plan of 2018 prepared by the Government of India states
that the country does not need additional non-renewable power plants in the
utility sector until 2027, with the commissioning of 50,025 MW coal-based
power plants under construction and achieving 275,000 MW total installed
renewable power capacity after retirement of nearly 48,000 MW old coal fired
plants.
Due to shortage of electricity, power cuts are common throughout India and this
has adversely effected the country’s economic growth. Theft of electricity,
common in most parts of urban India, amounts to 1.5% of India’s GDP. Despite
an ambitious rural electrification program, some 400 million Indians lose
electricity access during blackouts. While 84.9% of Indian villages have at least
an electricity line, just 46 percent of rural households have access to electricity.
About 57% of the electricity consumed in India is generated by thermal power
plants, 18% by hydroelectric power plants, 3% by nuclear power plants and
rest by 12% from other alternate sources like solar, wind, biomass etc, 9% from
gases. 53.7% of India’s commercial energy demand is met through the
country’s vast coal reserves. The country has also invested heavily in recent
years on renewable sources of energy such as wind energy.
households, industries and commercial establishments by creating and
improving necessary infrastructure. It is a joint collaboration of the Government
of India with states to share funding and create overall economic growth.
India's electricity sector is dominated by fossil fuels, and in particular coal,
which in 2017-18 produced about three fourths of all electricity. However, the
government is pushing for an increased investment in renewable energy. The
National Electricity Plan of 2018 prepared by the Government of India states
that the country does not need additional non-renewable power plants in the
utility sector until 2027, with the commissioning of 50,025 MW coal-based
power plants under construction and achieving 275,000 MW total installed
renewable power capacity after retirement of nearly 48,000 MW old coal fired
plants.
Due to shortage of electricity, power cuts are common throughout India and this
has adversely effected the country’s economic growth. Theft of electricity,
common in most parts of urban India, amounts to 1.5% of India’s GDP. Despite
an ambitious rural electrification program, some 400 million Indians lose
electricity access during blackouts. While 84.9% of Indian villages have at least
an electricity line, just 46 percent of rural households have access to electricity.
About 57% of the electricity consumed in India is generated by thermal power
plants, 18% by hydroelectric power plants, 3% by nuclear power plants and
rest by 12% from other alternate sources like solar, wind, biomass etc, 9% from
gases. 53.7% of India’s commercial energy demand is met through the
country’s vast coal reserves. The country has also invested heavily in recent
years on renewable sources of energy such as wind energy.
The total installed power generation capacity is sum of utility capacity, captive
power capacity and other non-utilities.
Total installed utility power capacity with sector wise & type wise break up
Secto
r
Thermal (MW)
Nuclea
r
(MW)
Renewable (MW)
Total
(MW)
%
Coal Gas
Diese
l
Sub-Total
Thermal
Hydro
Other
Renewab
le
State
64,456.5
0
7,078.95
363.9
3
71,899.3
8
0.00
29,858.0
0
2,003.37
103,760.
75
30
Centr
al
56,955.0
0
7,237.91 0.00
64,192.9
1
6,780.0
0
12,041.4
2
1,502.30
84,516.6
3
25
Privat
e
75,546.0
0
10,580.6
0
473.7
0
86,600.3
0
0.00 3,394.00 65,516.72
155,511.
02
45
All
India
196,957.
50
24,897.4
6
837.6
3
222,692.
59
6,780.0
0
45,293.4
2
69,022.39
343,788.
39
10
0
Captive power plant:-
A captive power plant also called auto producer or embedded generation is
a power generation facility used and managed by an industrial or commercial
energy user for their own energy consumption . Captive power plants can
operate off-grid or they can be connected to the electric grid to exchange excess
generation.
power capacity and other non-utilities.
Total installed utility power capacity with sector wise & type wise break up
Secto
r
Thermal (MW)
Nuclea
r
(MW)
Renewable (MW)
Total
(MW)
%
Coal Gas
Diese
l
Sub-Total
Thermal
Hydro
Other
Renewab
le
State
64,456.5
0
7,078.95
363.9
3
71,899.3
8
0.00
29,858.0
0
2,003.37
103,760.
75
30
Centr
al
56,955.0
0
7,237.91 0.00
64,192.9
1
6,780.0
0
12,041.4
2
1,502.30
84,516.6
3
25
Privat
e
75,546.0
0
10,580.6
0
473.7
0
86,600.3
0
0.00 3,394.00 65,516.72
155,511.
02
45
All
India
196,957.
50
24,897.4
6
837.6
3
222,692.
59
6,780.0
0
45,293.4
2
69,022.39
343,788.
39
10
0
Captive power plant:-
A captive power plant also called auto producer or embedded generation is
a power generation facility used and managed by an industrial or commercial
energy user for their own energy consumption . Captive power plants can
operate off-grid or they can be connected to the electric grid to exchange excess
generation.
The installed captive power generation capacity (above 1 MW capacity) in the
industries is 54,997 MW as on 31 March 2018 and generated 183,000 GWh
during the fiscal year 2017-18. Another 75,000 MW capacity diesel power
generation sets (excluding sets of size above 1 MW and below 100 kVA) are
also installed in the country. In addition, there are innumerable DG sets of
capacity less than 100 kVA to cater to emergency power needs during
the power outages in all sectors such as industrial, commercial, domestic and
agriculture.
Source
Captive Power
Capacity (MW)
Share
Electricity
generated (GWh)
Share
Coal 32,843 59.72% 147,036 80.35%
Hydroelectricity 70 0.13% 148 0.09%
Renewable energy
source
1540 2.80% 2,461 1.34%
Natural Gas 6,225 11.32% 23,316 12.74%
Oil 14,318 26.03% 10,038 5.49%
Total 54,997 100.00% 183,000
100.00%
industries is 54,997 MW as on 31 March 2018 and generated 183,000 GWh
during the fiscal year 2017-18. Another 75,000 MW capacity diesel power
generation sets (excluding sets of size above 1 MW and below 100 kVA) are
also installed in the country. In addition, there are innumerable DG sets of
capacity less than 100 kVA to cater to emergency power needs during
the power outages in all sectors such as industrial, commercial, domestic and
agriculture.
Source
Captive Power
Capacity (MW)
Share
Electricity
generated (GWh)
Share
Coal 32,843 59.72% 147,036 80.35%
Hydroelectricity 70 0.13% 148 0.09%
Renewable energy
source
1540 2.80% 2,461 1.34%
Natural Gas 6,225 11.32% 23,316 12.74%
Oil 14,318 26.03% 10,038 5.49%
Total 54,997 100.00% 183,000
100.00%
Electrical Transmission:-
Transmission of electricity is defined as bulk transfer of power over a long
distance at high voltage, generally of 132kV and above 765kv. The entire
country has been divided into five regions for transmission systems,
namely, Northern Region, North Eastern Region, Eastern Region, Southern
Region and Western Region. The Interconnected transmission system within
each region is also called the regional grid
.
The transmission system planning in the country, in the past, had traditionally
been linked to generation projects as part of the evacuation system. Ability of
the power system to safely withstand a contingency without generation
rescheduling or load-shedding was the main criteria for planning the
transmission system. However, due to various reasons such as spatial
development of load in the network, non-commissioning of load center
generating units originally planned and deficit in reactive compensation, certain
pockets in the power system could not safely operate even under normal
conditions. This had necessitated backing down of generation and operating at a
lower load generation balance in the past. Transmission planning has therefore
moved away from the earlier generation evacuation system planning to integrate
system planning.
While the predominant technology for electricity transmission and distribution
has been Alternating Current (AC) technology, High Voltage Direct Current
(HVDC) technology has also been used for interconnection of all regional grids
across the country and for bulk transmission of power over long distances.
Certain provisions in the Electricity Act 2003 such as open access to the
transmission and distribution network, recognition of power trading as a distinct
activity, the liberal definition of a captive generating plant and provision for
supply in rural areas are expected to introduce and encourage competition in the
electricity sector. It is expected that all the above measures on the generation,
transmission and distribution front would result in formation of a robust
electricity grid in the country.
Transmission of electricity is defined as bulk transfer of power over a long
distance at high voltage, generally of 132kV and above 765kv. The entire
country has been divided into five regions for transmission systems,
namely, Northern Region, North Eastern Region, Eastern Region, Southern
Region and Western Region. The Interconnected transmission system within
each region is also called the regional grid
.
The transmission system planning in the country, in the past, had traditionally
been linked to generation projects as part of the evacuation system. Ability of
the power system to safely withstand a contingency without generation
rescheduling or load-shedding was the main criteria for planning the
transmission system. However, due to various reasons such as spatial
development of load in the network, non-commissioning of load center
generating units originally planned and deficit in reactive compensation, certain
pockets in the power system could not safely operate even under normal
conditions. This had necessitated backing down of generation and operating at a
lower load generation balance in the past. Transmission planning has therefore
moved away from the earlier generation evacuation system planning to integrate
system planning.
While the predominant technology for electricity transmission and distribution
has been Alternating Current (AC) technology, High Voltage Direct Current
(HVDC) technology has also been used for interconnection of all regional grids
across the country and for bulk transmission of power over long distances.
Certain provisions in the Electricity Act 2003 such as open access to the
transmission and distribution network, recognition of power trading as a distinct
activity, the liberal definition of a captive generating plant and provision for
supply in rural areas are expected to introduce and encourage competition in the
electricity sector. It is expected that all the above measures on the generation,
transmission and distribution front would result in formation of a robust
electricity grid in the country.
Electrical Distribution:-
The total installed generating capacity in the country is 364.4 GW ,and the total
number of consumers is over 146 million. Apart from an extensive transmission
system network at 500kV HVDC, 400kV, 220kV, 132kV and 66kV which has
developed to transmit the power from generating station to the grid substations,
a vast network of sub transmission in distribution system has also come up for
utilisation of the power by the ultimate consumers.
However, due to lack of adequate investment on transmission and distribution
(T&D) works, the T&D losses have been consistently on higher side, and
reached to the level of 28.44% in the year 2008-09.The reduction of these losses
was essential to bring economic viability to the State Utilities.
As the T&D loss was not able to capture all the losses in the net work, concept
of Aggregate Technical and Commercial (AT&C) loss was introduced. AT&C
loss captures technical as well as commercial losses in the network and is a true
indicator of total losses in the system.
High technical losses in the system are primarily due to inadequate investments
over the years for system improvement works, which has resulted in unplanned
extensions of the distribution lines, overloading of the system elements like
transformers and conductors, and lack of adequate reactive power support.
The commercial losses are mainly due to low metering efficiency, theft &
pilferages. This may be eliminated by improving metering efficiency, proper
energy accounting & auditing and improved billing & collection efficiency.
Fixing of accountability of the personnel / feeder managers may help
considerably in reduction of AT&C loss.
The main objective of the programme was to bring Aggregate Technical &
Commercial (AT&C) losses below 15% in five years in urban and in high-
density areas.
The total installed generating capacity in the country is 364.4 GW ,and the total
number of consumers is over 146 million. Apart from an extensive transmission
system network at 500kV HVDC, 400kV, 220kV, 132kV and 66kV which has
developed to transmit the power from generating station to the grid substations,
a vast network of sub transmission in distribution system has also come up for
utilisation of the power by the ultimate consumers.
However, due to lack of adequate investment on transmission and distribution
(T&D) works, the T&D losses have been consistently on higher side, and
reached to the level of 28.44% in the year 2008-09.The reduction of these losses
was essential to bring economic viability to the State Utilities.
As the T&D loss was not able to capture all the losses in the net work, concept
of Aggregate Technical and Commercial (AT&C) loss was introduced. AT&C
loss captures technical as well as commercial losses in the network and is a true
indicator of total losses in the system.
High technical losses in the system are primarily due to inadequate investments
over the years for system improvement works, which has resulted in unplanned
extensions of the distribution lines, overloading of the system elements like
transformers and conductors, and lack of adequate reactive power support.
The commercial losses are mainly due to low metering efficiency, theft &
pilferages. This may be eliminated by improving metering efficiency, proper
energy accounting & auditing and improved billing & collection efficiency.
Fixing of accountability of the personnel / feeder managers may help
considerably in reduction of AT&C loss.
The main objective of the programme was to bring Aggregate Technical &
Commercial (AT&C) losses below 15% in five years in urban and in high-
density areas.
OVERVIEW OF NTPC IN INDIA: -
National Thermal Power Corporation Limited, is an Indian Public Sector
Undertaking, engaged in the business of generation of electricity and allied
activities.
It is a company incorporated under the Companies Act 1956 and is promoted
by the Government of India. The headquarters of the company is situated
at New Delhi. NTPC's core business is generation and sale of electricity to state-
owned power distribution companies and State Electricity Boards in India
NTPC is India’s largest energy company with roots planted way back in 1975 to
accelerate power development in India. Since then it has established itself as the
dominant power major with presence in the entire value chain of the power
generation business. From fossil fuels it has forayed into generating electricity
via hydro, nuclear and renewable energy sources. This foray will play a major
role in lowering its carbon footprint by reducing green house gas emissions. To
strengthen its core business, the corporation has diversified into the fields of
consultancy, power trading, training of power professionals, rural
electrification, ash utilisation and coal mining as well.
NTPC became a Maharatna company in May 2010, one of the only four
companies to be awarded this status. NTPC was ranked 512
th
in the ‘2018,
Forbes Global 2000’ ranking of the World’s biggest companies.
Growth of NTPC installed capacity and generation
National Thermal Power Corporation Limited, is an Indian Public Sector
Undertaking, engaged in the business of generation of electricity and allied
activities.
It is a company incorporated under the Companies Act 1956 and is promoted
by the Government of India. The headquarters of the company is situated
at New Delhi. NTPC's core business is generation and sale of electricity to state-
owned power distribution companies and State Electricity Boards in India
NTPC is India’s largest energy company with roots planted way back in 1975 to
accelerate power development in India. Since then it has established itself as the
dominant power major with presence in the entire value chain of the power
generation business. From fossil fuels it has forayed into generating electricity
via hydro, nuclear and renewable energy sources. This foray will play a major
role in lowering its carbon footprint by reducing green house gas emissions. To
strengthen its core business, the corporation has diversified into the fields of
consultancy, power trading, training of power professionals, rural
electrification, ash utilisation and coal mining as well.
NTPC became a Maharatna company in May 2010, one of the only four
companies to be awarded this status. NTPC was ranked 512
th
in the ‘2018,
Forbes Global 2000’ ranking of the World’s biggest companies.
Growth of NTPC installed capacity and generation
The total installed capacity of the company is 52,946 MW with 20 coal based,
7 gas based stations, 1 Hydro based station and 1 Wind based station. 9 Joint
Venture stations are coal based and 11 Solar PV projects. The capacity will
have a diversified fuel mix and by 2032, non fossil fuel based generation
capacity shall make up nearly 30% of NTPC’s portfolio.
NTPC has been operating its plants at high efficiency levels. Although the
company has 15.56% of the total national capacity, it contributes 22.74% of
total power generation due to its focus on high efficiency.
In October 2004, NTPC launched its Initial Public Offering (IPO) consisting of
5.25% as fresh issue and 5.25% as offer for sale by the Government of India.
NTPC thus became a listed company in November 2004 with the Government
holding 89.5% of the equity share capital. In February 2010, the Shareholding
of Government of India was reduced from 89.5% to 84.5% through a further
public offer. Government of India has further divested 9.5% shares through
OFS route in February 2013. With this, GOI's holding in NTPC has reduced
from 84.5% to 75%. The rest is held by Institutional Investors, banks and
Public. Presently, Government of India is holding in NTPC has reduced to
69.74%.
7 gas based stations, 1 Hydro based station and 1 Wind based station. 9 Joint
Venture stations are coal based and 11 Solar PV projects. The capacity will
have a diversified fuel mix and by 2032, non fossil fuel based generation
capacity shall make up nearly 30% of NTPC’s portfolio.
NTPC has been operating its plants at high efficiency levels. Although the
company has 15.56% of the total national capacity, it contributes 22.74% of
total power generation due to its focus on high efficiency.
In October 2004, NTPC launched its Initial Public Offering (IPO) consisting of
5.25% as fresh issue and 5.25% as offer for sale by the Government of India.
NTPC thus became a listed company in November 2004 with the Government
holding 89.5% of the equity share capital. In February 2010, the Shareholding
of Government of India was reduced from 89.5% to 84.5% through a further
public offer. Government of India has further divested 9.5% shares through
OFS route in February 2013. With this, GOI's holding in NTPC has reduced
from 84.5% to 75%. The rest is held by Institutional Investors, banks and
Public. Presently, Government of India is holding in NTPC has reduced to
69.74%.
NTPC operates from 55 locations in India, one location in Sri Lanka and 2
locations in Bangladesh.
Headquarters: In India, it has 8 regional headquarters (HQ):
Sr.
No.
Headquarter
s
City
1 NCRHQ Delhi
2 ER-I HQ Patna
3 ER-II HQ Bhubaneshwar
4 NRHQ Lucknow
5 SRHQ Secunderabad
6 WR-I HQ Mumbai
7 WR-II HQ Raipur
8 Hydro HQ
Delhi
locations in Bangladesh.
Headquarters: In India, it has 8 regional headquarters (HQ):
Sr.
No.
Headquarter
s
City
1 NCRHQ Delhi
2 ER-I HQ Patna
3 ER-II HQ Bhubaneshwar
4 NRHQ Lucknow
5 SRHQ Secunderabad
6 WR-I HQ Mumbai
7 WR-II HQ Raipur
8 Hydro HQ
Delhi
NTPC PLANTS AND THEIR CAPACITY:-
The total installed capacity of the company is 49,943 MW (including
JVs) with own 18 coal-based and 7 gas-based stations and 6 coal-based
and 1 gas-based in JV/subsidiary companies, located across the
country. Also 1 hydro-based station and 1 wind-based station. Nine joint
venture stations are coal-based and 11 solar PV projects.
(a) Coal-based thermal power plants
Sr.
No
.
Project State
Capacity M
W
Units Status
1
Singrauli
Super
Thermal
Power
Station
Uttar
Pradesh
2,000
5x200
MW,
2x500
MW
All units
functional
2
NTPC
Korba
Chhattisgar
h
2,600
3x200
MW,
4x500
MW
All units
functional
3
NTPC
Ramagunda
m
Telangana 2,600
3x200
MW,
4x500
MW
All units
functional.
4.
Farakka
Super
Thermal
Power
Station
West
Bengal
2,100
3x200
MW,
3x500
MW
All units
functional
The total installed capacity of the company is 49,943 MW (including
JVs) with own 18 coal-based and 7 gas-based stations and 6 coal-based
and 1 gas-based in JV/subsidiary companies, located across the
country. Also 1 hydro-based station and 1 wind-based station. Nine joint
venture stations are coal-based and 11 solar PV projects.
(a) Coal-based thermal power plants
Sr.
No
.
Project State
Capacity M
W
Units Status
1
Singrauli
Super
Thermal
Power
Station
Uttar
Pradesh
2,000
5x200
MW,
2x500
MW
All units
functional
2
NTPC
Korba
Chhattisgar
h
2,600
3x200
MW,
4x500
MW
All units
functional
3
NTPC
Ramagunda
m
Telangana 2,600
3x200
MW,
4x500
MW
All units
functional.
4.
Farakka
Super
Thermal
Power
Station
West
Bengal
2,100
3x200
MW,
3x500
MW
All units
functional
Sr.
No
.
Project State
Capacity M
W
Units Status
5
Vindhyachal
Super
Thermal
Power
Station
Madhya
Pradesh
4,760
6x210
MW,
7x500
MW
All units
functional.
Largest Thermal
Power Station of
India
6
Rihand
Thermal
Power
Station
Uttar
Pradesh
3,000
6x500
MW
All units
functional
7
Kahalgaon
Super
Thermal
Power
Station
Bihar 2,340
4x210
MW,
3x500
MW
All units
functional
8 NTPC Dadri
Uttar
Pradesh
1,820
4x210
MW,
2x490
MW
All units
functional
9
Talcher
Super
Thermal
Power
Station
Odisha 3,000
6x500
MW
All units
functional
No
.
Project State
Capacity M
W
Units Status
5
Vindhyachal
Super
Thermal
Power
Station
Madhya
Pradesh
4,760
6x210
MW,
7x500
MW
All units
functional.
Largest Thermal
Power Station of
India
6
Rihand
Thermal
Power
Station
Uttar
Pradesh
3,000
6x500
MW
All units
functional
7
Kahalgaon
Super
Thermal
Power
Station
Bihar 2,340
4x210
MW,
3x500
MW
All units
functional
8 NTPC Dadri
Uttar
Pradesh
1,820
4x210
MW,
2x490
MW
All units
functional
9
Talcher
Super
Thermal
Power
Station
Odisha 3,000
6x500
MW
All units
functional
Sr.
No
.
Project State
Capacity M
W
Units Status
10
Feroze
Gandhi
Unchahar
Thermal
Power
Station
Uttar
Pradesh
1,550
5x210
MW
1×500
MW
All units
functional
11
Talcher
Thermal
Power
Station
Odisha 460
4x60 MW,
2x110
MW
All units
functional
12
Simhadri
Super
Thermal
Power
Station
Andhra
Pradesh
2,000
4x500
MW
All units
functional
13
Tanda
Thermal
Power
Station
Uttar
Pradesh
1,760
4x110
MW
2×660
MW
4x110 MW
Units functional,
2×660 MW Unit
Under
Construction
14
Badarpur
Thermal
Power
Station
Delhi 705
3x95 MW,
2x210
MW
All units retired.
No
.
Project State
Capacity M
W
Units Status
10
Feroze
Gandhi
Unchahar
Thermal
Power
Station
Uttar
Pradesh
1,550
5x210
MW
1×500
MW
All units
functional
11
Talcher
Thermal
Power
Station
Odisha 460
4x60 MW,
2x110
MW
All units
functional
12
Simhadri
Super
Thermal
Power
Station
Andhra
Pradesh
2,000
4x500
MW
All units
functional
13
Tanda
Thermal
Power
Station
Uttar
Pradesh
1,760
4x110
MW
2×660
MW
4x110 MW
Units functional,
2×660 MW Unit
Under
Construction
14
Badarpur
Thermal
Power
Station
Delhi 705
3x95 MW,
2x210
MW
All units retired.
Sr.
No
.
Project State
Capacity M
W
Units Status
15
Sipat
Thermal
Power
Station
Chhattisgar
h
2,980
2x500
MW,
3x660
MW
All units
functional
16
Mauda
Super
Thermal
Power
Station
Maharashtr
a
2,320
2x500
MW,
2x660
MW
All units
functional
17
Barh Super
Thermal
Power
Station
Bihar 3,300
3×660
MW
2x660
MW
2x660 MW
Functional,
Three more
units of 660
MW under
construction.
[17][1
8]
18
Kudgi Super
Thermal
Power
Station
Karnataka 2,400
3x800
MW
All Units
functional.
19
NTPC
Bongaigaon
Assam 750
3x250
MW
2x250 MW Unit
functional 1x250
MW Unit Under
construction.
No
.
Project State
Capacity M
W
Units Status
15
Sipat
Thermal
Power
Station
Chhattisgar
h
2,980
2x500
MW,
3x660
MW
All units
functional
16
Mauda
Super
Thermal
Power
Station
Maharashtr
a
2,320
2x500
MW,
2x660
MW
All units
functional
17
Barh Super
Thermal
Power
Station
Bihar 3,300
3×660
MW
2x660
MW
2x660 MW
Functional,
Three more
units of 660
MW under
construction.
[17][1
8]
18
Kudgi Super
Thermal
Power
Station
Karnataka 2,400
3x800
MW
All Units
functional.
19
NTPC
Bongaigaon
Assam 750
3x250
MW
2x250 MW Unit
functional 1x250
MW Unit Under
construction.
Sr.
No
.
Project State
Capacity M
W
Units Status
20
LARA
Super
Thermal
Power
Station
Chhattisgar
h
4,000
2x800
MW,
3x800
MW
Under
construction.
21
Solapur
Super
Thermal
Power
Station
Maharashtr
a
1,320
2x660
MW
1x660 MW unit
functional,
1x660 MW unit
under
construction.
22
Gadarwara
Super
Thermal
Power
Station
Madhya
Pradesh
3,200
2×800M
W, 2×800
MW
Under
Construction
23
North
Karanpura
Thermal
Power
Station
Jharkhand 1,980
3×660
MW
Under
Construction
24
Darlipali
Super
Thermal
Power
Station
Odisha 1,600
2×800
MW
Under
Construction
No
.
Project State
Capacity M
W
Units Status
20
LARA
Super
Thermal
Power
Station
Chhattisgar
h
4,000
2x800
MW,
3x800
MW
Under
construction.
21
Solapur
Super
Thermal
Power
Station
Maharashtr
a
1,320
2x660
MW
1x660 MW unit
functional,
1x660 MW unit
under
construction.
22
Gadarwara
Super
Thermal
Power
Station
Madhya
Pradesh
3,200
2×800M
W, 2×800
MW
Under
Construction
23
North
Karanpura
Thermal
Power
Station
Jharkhand 1,980
3×660
MW
Under
Construction
24
Darlipali
Super
Thermal
Power
Station
Odisha 1,600
2×800
MW
Under
Construction
Sr.
No
.
Project State
Capacity M
W
Units Status
25
Khargone
Super
Thermal
Power
Station
Madhya
Pradesh
1,320
2×660
MW
Under
construction
26
Telangana
Super
Thermal
Power
Project
Telangana 1,600
2×800
MW
Under
construction
(b) Coal-based (owned through JVs)
Sr.
No.
Name of the JV Location State
Inst.
capacity in
megawatts
1
NSPCL. Joint venture
with SAIL.
Durgapur West Bengal 120
2
NSPCL. Joint venture
with SAIL.
Rourkela Odisha 120
3
NSPCL. Joint venture
with SAIL.
Bhilai Chhattisgarh 574
4 NPGC. Joint venture with
Bihar State Electricity
Aurangabad Bihar 4380
No
.
Project State
Capacity M
W
Units Status
25
Khargone
Super
Thermal
Power
Station
Madhya
Pradesh
1,320
2×660
MW
Under
construction
26
Telangana
Super
Thermal
Power
Project
Telangana 1,600
2×800
MW
Under
construction
(b) Coal-based (owned through JVs)
Sr.
No.
Name of the JV Location State
Inst.
capacity in
megawatts
1
NSPCL. Joint venture
with SAIL.
Durgapur West Bengal 120
2
NSPCL. Joint venture
with SAIL.
Rourkela Odisha 120
3
NSPCL. Joint venture
with SAIL.
Bhilai Chhattisgarh 574
4 NPGC. Joint venture with
Bihar State Electricity
Aurangabad Bihar 4380
Sr.
No.
Name of the JV Location State
Inst.
capacity in
megawatts
Board.
5
Muzaffarpur Thermal Power
Station (MTPS). Joint
venture with Bihar State
Electricity Board.
Kanti Bihar 610
6
BRBCL Joint venture
with Indian Railways.
Nabinagar Bihar 1000
7
Aravali Power CPL JV with
HPGCL & IPGCL
Jhajjar Haryana 1500
8
NTECL JV with NTPC &
TNEB
Chennai Tamil Nadu 1500
9
Meja Thermal Power Station
JV with NTPC &
UPRVUNL
Allahabad
Uttar
Pradesh
1320
10
PUVNL(Patratu) Joint
venture with Jharkhand State
Electricity Board.
Patratu Jharkhand 4000
Total
9049
No.
Name of the JV Location State
Inst.
capacity in
megawatts
Board.
5
Muzaffarpur Thermal Power
Station (MTPS). Joint
venture with Bihar State
Electricity Board.
Kanti Bihar 610
6
BRBCL Joint venture
with Indian Railways.
Nabinagar Bihar 1000
7
Aravali Power CPL JV with
HPGCL & IPGCL
Jhajjar Haryana 1500
8
NTECL JV with NTPC &
TNEB
Chennai Tamil Nadu 1500
9
Meja Thermal Power Station
JV with NTPC &
UPRVUNL
Allahabad
Uttar
Pradesh
1320
10
PUVNL(Patratu) Joint
venture with Jharkhand State
Electricity Board.
Patratu Jharkhand 4000
Total
9049
(c) Gas-based thermal power plants
Sr.No. Power project State Capacity MW
1 Anta Rajasthan 413.33
2 Auraiya Uttar Pradesh 663.36
3 Kawas Gujarat 656.20
4 Dadri Uttar Pradesh 829.78
5 Jhanor-Gandhar Gujarat 657.39
6 Kayamkulam Kerala 359.58
7 Faridabad Haryana 431.59
Total
4,017.23
(d) Gas-based (owned through JVs)
Ratnagiri Gas and Power Private Limited (RGPPL) is joint venture project
with GAIL in Indian state of Maharashtra. Its installed capacity is 1967.08
MW.
(e) Hydro-electric power plants
The company has also stepped up its hydroelectric power (hydel) projects
implementation. Some of these projects are:
Sr.No. Power project State Capacity MW
1 Anta Rajasthan 413.33
2 Auraiya Uttar Pradesh 663.36
3 Kawas Gujarat 656.20
4 Dadri Uttar Pradesh 829.78
5 Jhanor-Gandhar Gujarat 657.39
6 Kayamkulam Kerala 359.58
7 Faridabad Haryana 431.59
Total
4,017.23
(d) Gas-based (owned through JVs)
Ratnagiri Gas and Power Private Limited (RGPPL) is joint venture project
with GAIL in Indian state of Maharashtra. Its installed capacity is 1967.08
MW.
(e) Hydro-electric power plants
The company has also stepped up its hydroelectric power (hydel) projects
implementation. Some of these projects are:
1. Loharinag Pala Hydro Power Project by NTPC Ltd: Loharinag Pala
Hydro Power Project (600 MW i.e.150 MW x 4 Units) is located on
river Bhagirathi (a tributary of the Ganges) in Uttarkashi district
of Uttarakhand state. This is the first project downstream from the origin
of the Ganges at Gangotri. Project was at advance stage of construction
when it was discontinued by Government of India in August 2010.
2. Tapovan Vishnugad 520MW Hydro Power Project by NTPC Ltd: In
Joshimath town. The project is under construction.
3. Lata Tapovan 130MW Hydro Power Project by NTPC Ltd: is further
upstream to Joshimath. This project is under environmental revision.
4. Koldam Dam Hydro Power Project 800 MW in Himachal
Pradesh (130 km from Chandigarh ).All unit of this project are under
commercial operation w.e.f. 18 July 2015.
5. Rupasiyabagar Khasiabara HPP, 261 MW in
Pithoragarh, Uttarakhand State, near China Border. This project is yet to
be given investment approval.
6. Singrauli CW Discharge (Small Hydro) 8 MW is under construction on
discharge canal of Singrauli Super Thermal Power Station in Uttar
Pradesh.
7. Rammam Hydro 120 MW run of the river is under construction project
on Rammam river at approx 150 km from Bagdogra / Siliguri in
Distt. Darjeeling in West Bengal.The Darjeeling town is 50 km from the
project. Solar photovoltaic power plants
NTPC has drafted its business plan of capacity addition of about 1,000 MW
through renewable resources by 2017. In this endeavour, NTPC has already
commissioned 845 MW Solar PV Projects.
Sr.No. Project State/UT Capacity
1 Dadri Solar PV Uttar Pradesh 05 MW
2 Portblair Solar PV Andaman & Nicobar Island 05 MW
3 Ramagundam Solar PV Telangana 10 MW
4 Talcher Kaniha Odisha 10 MW
Hydro Power Project (600 MW i.e.150 MW x 4 Units) is located on
river Bhagirathi (a tributary of the Ganges) in Uttarkashi district
of Uttarakhand state. This is the first project downstream from the origin
of the Ganges at Gangotri. Project was at advance stage of construction
when it was discontinued by Government of India in August 2010.
2. Tapovan Vishnugad 520MW Hydro Power Project by NTPC Ltd: In
Joshimath town. The project is under construction.
3. Lata Tapovan 130MW Hydro Power Project by NTPC Ltd: is further
upstream to Joshimath. This project is under environmental revision.
4. Koldam Dam Hydro Power Project 800 MW in Himachal
Pradesh (130 km from Chandigarh ).All unit of this project are under
commercial operation w.e.f. 18 July 2015.
5. Rupasiyabagar Khasiabara HPP, 261 MW in
Pithoragarh, Uttarakhand State, near China Border. This project is yet to
be given investment approval.
6. Singrauli CW Discharge (Small Hydro) 8 MW is under construction on
discharge canal of Singrauli Super Thermal Power Station in Uttar
Pradesh.
7. Rammam Hydro 120 MW run of the river is under construction project
on Rammam river at approx 150 km from Bagdogra / Siliguri in
Distt. Darjeeling in West Bengal.The Darjeeling town is 50 km from the
project. Solar photovoltaic power plants
NTPC has drafted its business plan of capacity addition of about 1,000 MW
through renewable resources by 2017. In this endeavour, NTPC has already
commissioned 845 MW Solar PV Projects.
Sr.No. Project State/UT Capacity
1 Dadri Solar PV Uttar Pradesh 05 MW
2 Portblair Solar PV Andaman & Nicobar Island 05 MW
3 Ramagundam Solar PV Telangana 10 MW
4 Talcher Kaniha Odisha 10 MW
5 Faridabad Solar PV Haryana 05 MW
6 Unchahar Solar PV Uttar Pradesh 10 MW
7 Rajgarh Solar PV Madhya Pradesh 50 MW
8 Singrauli Solar PV Uttar Pradesh 15 MW
9 Ananthpuram Solar PV Andhra Pradesh 250 MW
10 Bhadla-Solar PV Rajasthan 260 MW
11 Mandsaur-Solar PV Madhya Pradesh 250 MW
12 Total
870 MW
(f) Wind power
NTPC is installing a 50 MW wind power project at Rajmol in Gujarat state.
6 Unchahar Solar PV Uttar Pradesh 10 MW
7 Rajgarh Solar PV Madhya Pradesh 50 MW
8 Singrauli Solar PV Uttar Pradesh 15 MW
9 Ananthpuram Solar PV Andhra Pradesh 250 MW
10 Bhadla-Solar PV Rajasthan 260 MW
11 Mandsaur-Solar PV Madhya Pradesh 250 MW
12 Total
870 MW
(f) Wind power
NTPC is installing a 50 MW wind power project at Rajmol in Gujarat state.
VISION
A world class integrated power major, powering India's growth with increasing
global presence.
MISSION
Develop and provide reliable power related products and services at
competitive prices, integrating multiple energy resources with innovative &
Eco-friendly technologies and contribution to the society.
A world class integrated power major, powering India's growth with increasing
global presence.
MISSION
Develop and provide reliable power related products and services at
competitive prices, integrating multiple energy resources with innovative &
Eco-friendly technologies and contribution to the society.
NTPC KAWAS:-
NTPC Kawas is located at Aditya Nagar, in Surat district in the Indian
state of Gujarat.
The plant was establish in 1992 and cost of plant was 1600 crore .It was
completed with help of France company in 24 months.
The power plant is one of the gas based power plants of NTPC. The gas
for the power plant is sourced from GAIL(Gas Authority Of India
Limited) HBJ(Hazira –Bijapur-jagishpur) Pipeline - South Basin Gas
field. It’s come through the two pipeline 36’ an 42’ inch from bombay
high Basin offshore.
Sometime also uses Liquified natural Gas (LNG) which supplied from
Gujarat Gas.
It’s also Napatha base plant which uses naptaha in liquid form as a Fuel
which supplied by from HPCL/IOC
Price low for natural gas , Medium for LNG and Higher for napatha .
Due to use of dual fuel in Plant is also called as Dual Fuel Plant.
Source of water for the power plant is Hazira Branch Canal Singanpur
Weir.
Total Plant Capacity 656.2 MW with Two Combined Cycle power plant
15.7 Million (656.2 x1000x24) Maximum unit can be generated by plant
in one day.
Single Combine Cycle power plant capacity is 330.2 MW.
It’s consists of four Gas Turbine(GT) and Steam Turbine(ST) .
4 GT Capacity (106 x 4) are 424 MW and Two ST (116.1x2) are 232.2
MW
Currently Solar power installed in the Plant for own utility purpose.
4 GT having 4 cranking motors of 1 MW and 2 ST having 6 motors (3x2)
Circulating Water unit consists of 5 motors of 930 kW power (In 2 block
, each block having 2 motors and 1 standby motors)
NTPC kawas having maximum utility 8-10 MW(2 Generator
Transformers)
Generation Voltage at 220 kV and Transmitted to Power Grid.
NTPC Kawas is located at Aditya Nagar, in Surat district in the Indian
state of Gujarat.
The plant was establish in 1992 and cost of plant was 1600 crore .It was
completed with help of France company in 24 months.
The power plant is one of the gas based power plants of NTPC. The gas
for the power plant is sourced from GAIL(Gas Authority Of India
Limited) HBJ(Hazira –Bijapur-jagishpur) Pipeline - South Basin Gas
field. It’s come through the two pipeline 36’ an 42’ inch from bombay
high Basin offshore.
Sometime also uses Liquified natural Gas (LNG) which supplied from
Gujarat Gas.
It’s also Napatha base plant which uses naptaha in liquid form as a Fuel
which supplied by from HPCL/IOC
Price low for natural gas , Medium for LNG and Higher for napatha .
Due to use of dual fuel in Plant is also called as Dual Fuel Plant.
Source of water for the power plant is Hazira Branch Canal Singanpur
Weir.
Total Plant Capacity 656.2 MW with Two Combined Cycle power plant
15.7 Million (656.2 x1000x24) Maximum unit can be generated by plant
in one day.
Single Combine Cycle power plant capacity is 330.2 MW.
It’s consists of four Gas Turbine(GT) and Steam Turbine(ST) .
4 GT Capacity (106 x 4) are 424 MW and Two ST (116.1x2) are 232.2
MW
Currently Solar power installed in the Plant for own utility purpose.
4 GT having 4 cranking motors of 1 MW and 2 ST having 6 motors (3x2)
Circulating Water unit consists of 5 motors of 930 kW power (In 2 block
, each block having 2 motors and 1 standby motors)
NTPC kawas having maximum utility 8-10 MW(2 Generator
Transformers)
Generation Voltage at 220 kV and Transmitted to Power Grid.
Kawas Gas Power Plant is composed of two combined cycle modules
supplied by M/s GEC Alsthom – France.
Each modules consists of two Gas Turbine Generators 106 MW each),
two waste heat recovery boilers (CMI Belgium make) and one Steam
Turbine Generator 116.1 MW.
AN OVERVIEW OF KAWAS GAS POWER PLANT
Figure 1: Model of NTPC Kawas gas project plant
Approved capacity 645 MW
Installed Capacity 645 MW
supplied by M/s GEC Alsthom – France.
Each modules consists of two Gas Turbine Generators 106 MW each),
two waste heat recovery boilers (CMI Belgium make) and one Steam
Turbine Generator 116.1 MW.
AN OVERVIEW OF KAWAS GAS POWER PLANT
Figure 1: Model of NTPC Kawas gas project plant
Approved capacity 645 MW
Installed Capacity 645 MW
Location Surat , Gujrat
Gas Source HBJ Pipeline - South Basin Gas field
Water Source Hazira Branch Canal Singanpur Weir
Beneficiary States
Madhya Pradesh , Gujarat , Maharashtra, Goa,
Daman & Diu, Dadar Nagar Haveli, Chattisgarh
Approved Investment Rs. 1599.57 Crore
Unit Sizes 4X106 GT 2X110.5 ST
Units Commissioned
Unit I- 106 MW GT March 1992
Unit II- 106 MW GT May 1992
Unit III- 106 MW GT June 1992
Unit IV- 106 MW GT November 1992
Unit V- 110.5 MW ST February 1993
Unit VI- 110.5 MW ST March 1993
International Assistance France and Belgium
SALIENT FEATURES OF PLAN T:-
01) Gas Turbine : 106 MW, 3 Stage Impulse Type
02) GT Compressor : 17 Stages Axial Flow Compressor
03) Combustion Chambers : Cannular type with 2 Igniters and
14 Combustor baskets
04) Air filter type and Particle Size : Self cleaning inlet air filter, for
Removing 5 micron particle size and
Above and handling air flow 380 kg/sec.
05) Bypass Stack : Vertical circular 5.93 m dia. & 55 m height
06) Waste Heat Recovery Boiler : Double drum, non-firing, assisted
(WHRB) Circulation
Type heat recovery boiler
07) WHRB Steam Parameters : Press Flow Temperature (Kg/cm²)
(Ton/hr) (Deg. C.)
HP Steam 71.3 174 520
LP Steam 7.1 40 192
08) Steam Turbine : 116 MW, impulse, tandem
Compound, Double exhaust,
Condensing type, with HP Turbine
13 stage horizontal
Single flow LP Turbine 5 stage
horizontal double flow
09) Condenser : Two Pass Surface Condenser, each
having 9200 no
Gas Source HBJ Pipeline - South Basin Gas field
Water Source Hazira Branch Canal Singanpur Weir
Beneficiary States
Madhya Pradesh , Gujarat , Maharashtra, Goa,
Daman & Diu, Dadar Nagar Haveli, Chattisgarh
Approved Investment Rs. 1599.57 Crore
Unit Sizes 4X106 GT 2X110.5 ST
Units Commissioned
Unit I- 106 MW GT March 1992
Unit II- 106 MW GT May 1992
Unit III- 106 MW GT June 1992
Unit IV- 106 MW GT November 1992
Unit V- 110.5 MW ST February 1993
Unit VI- 110.5 MW ST March 1993
International Assistance France and Belgium
SALIENT FEATURES OF PLAN T:-
01) Gas Turbine : 106 MW, 3 Stage Impulse Type
02) GT Compressor : 17 Stages Axial Flow Compressor
03) Combustion Chambers : Cannular type with 2 Igniters and
14 Combustor baskets
04) Air filter type and Particle Size : Self cleaning inlet air filter, for
Removing 5 micron particle size and
Above and handling air flow 380 kg/sec.
05) Bypass Stack : Vertical circular 5.93 m dia. & 55 m height
06) Waste Heat Recovery Boiler : Double drum, non-firing, assisted
(WHRB) Circulation
Type heat recovery boiler
07) WHRB Steam Parameters : Press Flow Temperature (Kg/cm²)
(Ton/hr) (Deg. C.)
HP Steam 71.3 174 520
LP Steam 7.1 40 192
08) Steam Turbine : 116 MW, impulse, tandem
Compound, Double exhaust,
Condensing type, with HP Turbine
13 stage horizontal
Single flow LP Turbine 5 stage
horizontal double flow
09) Condenser : Two Pass Surface Condenser, each
having 9200 no
Stainless Steel Tubes
10) Generator rated output : 134 MVA for GT & 145 MVA for ST
Terminal voltage : 11.5 KV with Blushless Excitation
Rated speed : 3000 RPM
Type of cooling : Air-Cooled
11) Black start facility : 3 MW Diesel Generator Set
12) Cooling Tower type : Two Natural Draft Cooling Tower
(One for each module)
Cooling water (Design flow) : 24000 m³/hr
Range of cooling : 10 °C
Dimensions : 106.3 meters height & Base diameter of
92 m.
13) Cooling water pumps : 5 (one common standby)/11910 m³/hr &
Design
Parameters 22.4 MWC
14) Pre-treatment Plant : 2 Clariflocculators each rated for 1500
m³/hr
15) DM Water Plant : Two streams of 55 m³/hr
10) Generator rated output : 134 MVA for GT & 145 MVA for ST
Terminal voltage : 11.5 KV with Blushless Excitation
Rated speed : 3000 RPM
Type of cooling : Air-Cooled
11) Black start facility : 3 MW Diesel Generator Set
12) Cooling Tower type : Two Natural Draft Cooling Tower
(One for each module)
Cooling water (Design flow) : 24000 m³/hr
Range of cooling : 10 °C
Dimensions : 106.3 meters height & Base diameter of
92 m.
13) Cooling water pumps : 5 (one common standby)/11910 m³/hr &
Design
Parameters 22.4 MWC
14) Pre-treatment Plant : 2 Clariflocculators each rated for 1500
m³/hr
15) DM Water Plant : Two streams of 55 m³/hr
COMBINE CYCLE POWER PLANT
Combine cycle power plant integrates two power conversion cycle-Brayton
cycle (Gas turbine) and Rankine cycle (Steam turbine) with the principal
objective of increasing overall plant efficiency.
BRAYTON CYCLE
Gas turbine plants operate on this cycle in which air is compressed (process 1-
2, in P-V diagram of figure 2). This compressed air is heated in the combustor
by burning fuel, where plant of compressed air is used for combustion (process
2-3) and the flue gases produced are allowed to expand in the turbine (process
3-4), which is coupled with the generator. In modern gas turbines the
temperature of the exhaust gases is in the range of 500 °C to 550 ° C.
The conversion of heat energy to mechanical energy with the aid of steam is
based on this thermodynamic cycle. In its simplest form the cycle works as
follows:
The initial stage of working fluid is water (point 3 of figure 3), which at a
certain temperature is pressurized by a pump (process 3-4) and fed to the
boiler
In the boiler the pressurized water is heated at constant pressure (process
4-5-6-1)
Superheated steam (generated at point-1) is expanded in the turbine
(process1-2), which is coupled with generator. Modern steam power
Combine cycle power plant integrates two power conversion cycle-Brayton
cycle (Gas turbine) and Rankine cycle (Steam turbine) with the principal
objective of increasing overall plant efficiency.
BRAYTON CYCLE
Gas turbine plants operate on this cycle in which air is compressed (process 1-
2, in P-V diagram of figure 2). This compressed air is heated in the combustor
by burning fuel, where plant of compressed air is used for combustion (process
2-3) and the flue gases produced are allowed to expand in the turbine (process
3-4), which is coupled with the generator. In modern gas turbines the
temperature of the exhaust gases is in the range of 500 °C to 550 ° C.
The conversion of heat energy to mechanical energy with the aid of steam is
based on this thermodynamic cycle. In its simplest form the cycle works as
follows:
The initial stage of working fluid is water (point 3 of figure 3), which at a
certain temperature is pressurized by a pump (process 3-4) and fed to the
boiler
In the boiler the pressurized water is heated at constant pressure (process
4-5-6-1)
Superheated steam (generated at point-1) is expanded in the turbine
(process1-2), which is coupled with generator. Modern steam power
plants have steam temperature in the range of 500°C to 550 °C at the
inlet of the turbine.
COMBINING TWO CYCLES TO IMPROVE EFFICIE NCY
We have seen in the above two cycles that exhaust is at temperature of 500-550
°C and in Rankine cycle heat is required to generate steam at the temperature
of 500-550 °C. Therefore gas turbine exhaust heat can be recovered using a
waste heat recovery boiler to run a steam turbine on Rankine cycle.
If efficiency of gas turbine cycle (when natural gas is used as fuel) is 31% and
the efficiency of Rankine cycle is 35%, then overall efficiency comes to 49%.
Conventional fossil fuel fired boiler of the steam power plant is replaced with a
heat recovery steam generator (HRSG). Exhaust gas from the gas turbine is led
to the HRSG where heat in exhaust gas is utilized to produce steam at desired
parameters as required by the steam turbine.
inlet of the turbine.
COMBINING TWO CYCLES TO IMPROVE EFFICIE NCY
We have seen in the above two cycles that exhaust is at temperature of 500-550
°C and in Rankine cycle heat is required to generate steam at the temperature
of 500-550 °C. Therefore gas turbine exhaust heat can be recovered using a
waste heat recovery boiler to run a steam turbine on Rankine cycle.
If efficiency of gas turbine cycle (when natural gas is used as fuel) is 31% and
the efficiency of Rankine cycle is 35%, then overall efficiency comes to 49%.
Conventional fossil fuel fired boiler of the steam power plant is replaced with a
heat recovery steam generator (HRSG). Exhaust gas from the gas turbine is led
to the HRSG where heat in exhaust gas is utilized to produce steam at desired
parameters as required by the steam turbine.
GAS TURBINES: -
Evolution of gas turbines and combined cycle plants
Early History
Gas Turbines or Combustion turbines (an expression which has become popular
in past few years) were FIRST developed in the late 18th century. Patents for
modern versions of combustion turbines were awarded in late nineteenth
century to “Franze Stolze” and “Charles Curtis” , however all early versions of
gas turbines were impractical because the power necessary to drive compressors
outweighed the power generated by turbine. This is because of the fact that the
turbine inlet temperature (TIT) required delivering positive output and a certain
minimum acceptable efficiency was above the allowable temperatures that
could be faced by materials available in those days. For example in 1904 two
French engineers, Armengaud and Lemale built a unit, which did little more
than turn itself over. The reason – maximum temperature that could be used was
about 500 degree C and the compressor efficiency was abysmally low at 60 %.
Gas Turbine in its simplest form works on Joule Brayton Cycle, which
consists of following:
Compression (1-2): A rotating compressor acts as a fan to drive the working
fluid into the heating system. The fluid is pressurized adiabatically, thus its
temperature increases.
Combustion (2-3): The fluid is heated by internal combustion, in a continuous
process-taking place at constant pressure. A steady supply of fuel mixes with air
at high velocity from the compressor and burns as it flows through a flame
zone. Combustion occurs in a very small volume, partly because it takes place
at high pressure.
Expansion (3-4): The working fluid at high pressure is then released to the
turbine, which converts the fluid's energy into useful work as the temperature of
the working fluid decreases. Part of this work is returned to the compressor. The
remainder is used for the application intended: Generation of electricity,
pumping, and turbojet propulsion.
Evolution of gas turbines and combined cycle plants
Early History
Gas Turbines or Combustion turbines (an expression which has become popular
in past few years) were FIRST developed in the late 18th century. Patents for
modern versions of combustion turbines were awarded in late nineteenth
century to “Franze Stolze” and “Charles Curtis” , however all early versions of
gas turbines were impractical because the power necessary to drive compressors
outweighed the power generated by turbine. This is because of the fact that the
turbine inlet temperature (TIT) required delivering positive output and a certain
minimum acceptable efficiency was above the allowable temperatures that
could be faced by materials available in those days. For example in 1904 two
French engineers, Armengaud and Lemale built a unit, which did little more
than turn itself over. The reason – maximum temperature that could be used was
about 500 degree C and the compressor efficiency was abysmally low at 60 %.
Gas Turbine in its simplest form works on Joule Brayton Cycle, which
consists of following:
Compression (1-2): A rotating compressor acts as a fan to drive the working
fluid into the heating system. The fluid is pressurized adiabatically, thus its
temperature increases.
Combustion (2-3): The fluid is heated by internal combustion, in a continuous
process-taking place at constant pressure. A steady supply of fuel mixes with air
at high velocity from the compressor and burns as it flows through a flame
zone. Combustion occurs in a very small volume, partly because it takes place
at high pressure.
Expansion (3-4): The working fluid at high pressure is then released to the
turbine, which converts the fluid's energy into useful work as the temperature of
the working fluid decreases. Part of this work is returned to the compressor. The
remainder is used for the application intended: Generation of electricity,
pumping, and turbojet propulsion.
fig 6 fig7
The use of a compressible gas such as air as working fluid permits the
absorption and release of considerable amounts of energy. Such energy is
basically the kinetic energy of its molecules, which is proportional to its
temperature. Ideal gas turbine cycles are based on the Joule or Brayton
cycles, i.e., compression and expansion at constant entropy, and heat addition
and release at constant pressure.
In an ideal cycle, efficiency varies with the temperature ratio of the working
fluid in the compression process, which is related to its pressure ratio. The inlet
temperature in the turbine section is generally limited by turbine technology,
materials strength, corrosion and other considerations. The increment of
temperature also depends on the initial temperature of the working fluid. Some
effects must be considered which diminish efficiency in real operating cycles,
such as inefficiency in compression and expansion, loss of pressure during heat
addition and rejection, variation of working fluid specific heat with temperature,
incomplete combustion, etc.
Gas Turbine Design Advancements:
In gas turbine design the firing temperature, compression ratio, mass flow, and
centrifugal stresses are the factors limiting both unit size and efficiency. For
example, each 55°C increase in firing temperature gives a 10 - 13 percent output
increase and a 2 - 4 percent efficiency increase. The most critical areas in the
gas turbine determining the engine efficiency and life are the hot gas path, i.e.,
the combustion chambers and the turbine first stage stationary nozzles and
rotating buckets. The development process takes time, however, because each
change of material may require years of laboratory and field tests to ensure its
suitability in terms of creep strength, yield limit, fatigue strength, oxidation
resistance, corrosion resistance, thermal cycling effects, etc.
The use of a compressible gas such as air as working fluid permits the
absorption and release of considerable amounts of energy. Such energy is
basically the kinetic energy of its molecules, which is proportional to its
temperature. Ideal gas turbine cycles are based on the Joule or Brayton
cycles, i.e., compression and expansion at constant entropy, and heat addition
and release at constant pressure.
In an ideal cycle, efficiency varies with the temperature ratio of the working
fluid in the compression process, which is related to its pressure ratio. The inlet
temperature in the turbine section is generally limited by turbine technology,
materials strength, corrosion and other considerations. The increment of
temperature also depends on the initial temperature of the working fluid. Some
effects must be considered which diminish efficiency in real operating cycles,
such as inefficiency in compression and expansion, loss of pressure during heat
addition and rejection, variation of working fluid specific heat with temperature,
incomplete combustion, etc.
Gas Turbine Design Advancements:
In gas turbine design the firing temperature, compression ratio, mass flow, and
centrifugal stresses are the factors limiting both unit size and efficiency. For
example, each 55°C increase in firing temperature gives a 10 - 13 percent output
increase and a 2 - 4 percent efficiency increase. The most critical areas in the
gas turbine determining the engine efficiency and life are the hot gas path, i.e.,
the combustion chambers and the turbine first stage stationary nozzles and
rotating buckets. The development process takes time, however, because each
change of material may require years of laboratory and field tests to ensure its
suitability in terms of creep strength, yield limit, fatigue strength, oxidation
resistance, corrosion resistance, thermal cycling effects, etc.
The figure shows how overall (net) efficiency of simple and combined-cycle
power plants has improved since 1950. The efficiency of simple cycle gas
turbine plants has doubled, and with the advent of combined-cycle plants,
efficiency has tripled in the past fifty years. Turbine nozzles and buckets are
cast from nickel super alloys and are coated under vacuum with special metals
to resist the hot corrosion that occurs. The high temperatures encountered in the
first stage of the turbine are of great importance, particularly if contaminants
such as sodium, vanadium and potassium are present. Only a few parts per
million of these contaminants can cause hot corrosion of uncoated components
at the high firing temperature encountered. With proper coating of nozzles and
buckets and treatment of fuels to minimize the contaminants, manufacturers
claim the hot-gas-path components should last 30,000 to 40,000 hours of
operation before replacement, particularly the hot-gas-path parts, that give rise
to the relatively high maintenance cost for gas turbines (typical O&M annual
costs 5 percent of the capital cost).
power plants has improved since 1950. The efficiency of simple cycle gas
turbine plants has doubled, and with the advent of combined-cycle plants,
efficiency has tripled in the past fifty years. Turbine nozzles and buckets are
cast from nickel super alloys and are coated under vacuum with special metals
to resist the hot corrosion that occurs. The high temperatures encountered in the
first stage of the turbine are of great importance, particularly if contaminants
such as sodium, vanadium and potassium are present. Only a few parts per
million of these contaminants can cause hot corrosion of uncoated components
at the high firing temperature encountered. With proper coating of nozzles and
buckets and treatment of fuels to minimize the contaminants, manufacturers
claim the hot-gas-path components should last 30,000 to 40,000 hours of
operation before replacement, particularly the hot-gas-path parts, that give rise
to the relatively high maintenance cost for gas turbines (typical O&M annual
costs 5 percent of the capital cost).
GAS TURBINE PLANT:-
Introduction:
The gas turbine is a common form of heat engine working with a series of
processes consisting of compression of air taken from atmosphere, increase of
working medium temperature by constant pressure ignition of fuel in
combustion chamber, expansion of SI and IC engines in working medium and
combustion, but it is like steam turbine in its aspect of the steady flow of the
working medium. It was in 1939, Brown Beaver developed the first industrial
duty gas turbine. The output being 4000 KW with open cycle efficiency of
18%. The development in the science of aerodynamics and metallurgy
significantly contributed to increased compression and expansion efficiency in
the recent years.
At Kawas, the GE-Alsthom make Gas Turbine (Model 9E) has an operating
efficiency of 31% and 49% in open cycle and combined cycle mode
respectively when natural gas is used as fuel. Today gas turbine unit sizes with
output above 250 MW at ISO conditions have been designed and developed.
Thus the advances in metallurgical technology have brought with a good
competitive edge over conventional steam cycle power plant.
Kawas Gas Turbine Plant:
The modern gas turbine plants are commonly available in package form with
few functional sub assemblies.
Advantages of gas turbine plant:-
Some of the advantages are quite obvious, such as fast operation, minimum site
investment.
Low installation cost owing to standardization, factory assembly and test.
This makes the
installation of the station easy and keeps the cost per installed kilowatt low
because the package power station is quickly ready to be put in operation.
Site implementation includes one simple and robust structure to get unit
alignment.
Introduction:
The gas turbine is a common form of heat engine working with a series of
processes consisting of compression of air taken from atmosphere, increase of
working medium temperature by constant pressure ignition of fuel in
combustion chamber, expansion of SI and IC engines in working medium and
combustion, but it is like steam turbine in its aspect of the steady flow of the
working medium. It was in 1939, Brown Beaver developed the first industrial
duty gas turbine. The output being 4000 KW with open cycle efficiency of
18%. The development in the science of aerodynamics and metallurgy
significantly contributed to increased compression and expansion efficiency in
the recent years.
At Kawas, the GE-Alsthom make Gas Turbine (Model 9E) has an operating
efficiency of 31% and 49% in open cycle and combined cycle mode
respectively when natural gas is used as fuel. Today gas turbine unit sizes with
output above 250 MW at ISO conditions have been designed and developed.
Thus the advances in metallurgical technology have brought with a good
competitive edge over conventional steam cycle power plant.
Kawas Gas Turbine Plant:
The modern gas turbine plants are commonly available in package form with
few functional sub assemblies.
Advantages of gas turbine plant:-
Some of the advantages are quite obvious, such as fast operation, minimum site
investment.
Low installation cost owing to standardization, factory assembly and test.
This makes the
installation of the station easy and keeps the cost per installed kilowatt low
because the package power station is quickly ready to be put in operation.
Site implementation includes one simple and robust structure to get unit
alignment.
Transport: Package concept makes easier shipping, handling, because of
its robustness.
Low standby cost: fast start up and shut down reduce conventional stand
by cost.
The power requirements to keep the plant in standby condition are
significantly lower than those for other types of prime movers.
Maximum application flexibility: The package plant may be operated
either in parallel with existing plants or as a completely isolated station.
These units have been used, widely for base, peaking and even
emergency service. The station can be equipped with remote control for
starting, synchronizing & loading.
STEAM TURBINE:
The steam turbine is yet another important part of the plant. The combined use
of boiler and steam turbine makes the plant efficiency better.
The HP turbine is a single flow horizontal split type with 13 stages whereas the
LP module is double flow horizontal split type with 5 blades at each side. There
are 6 bearings along from the high pressure turbine to the generator. The output
of ST is 116.6MW at 11KV.
Various sensors are mounted on bearing number 1 i.e. before HP turbine such as
vibration sensors to measure rotor and stator expansion, sensors for measuring
axial movement. Measurement of these parameters is very critical since the
spacing between rotor and stator is about 6mm.
its robustness.
Low standby cost: fast start up and shut down reduce conventional stand
by cost.
The power requirements to keep the plant in standby condition are
significantly lower than those for other types of prime movers.
Maximum application flexibility: The package plant may be operated
either in parallel with existing plants or as a completely isolated station.
These units have been used, widely for base, peaking and even
emergency service. The station can be equipped with remote control for
starting, synchronizing & loading.
STEAM TURBINE:
The steam turbine is yet another important part of the plant. The combined use
of boiler and steam turbine makes the plant efficiency better.
The HP turbine is a single flow horizontal split type with 13 stages whereas the
LP module is double flow horizontal split type with 5 blades at each side. There
are 6 bearings along from the high pressure turbine to the generator. The output
of ST is 116.6MW at 11KV.
Various sensors are mounted on bearing number 1 i.e. before HP turbine such as
vibration sensors to measure rotor and stator expansion, sensors for measuring
axial movement. Measurement of these parameters is very critical since the
spacing between rotor and stator is about 6mm.
GENERATOR
The basic function of the generator is to convert mechanical power, delivered
from the shaft of the turbine, into electrical power. Therefore a generator is
actually a rotating mechanical energy converter. The mechanical energy from
the turbine is converted by means of a rotating magnetic field produced by
direct current in the copper winding of the rotor or field, which generates three-
phase alternating currents and voltages in the copper winding of the stator
(armature).
The generators particular to this category are of the two- and four-pole design
employing round-rotors, with rotational operating speeds of 3600 and 1800rpm
in North America, parts of Japan, and Asia (3000 and 1500 rpm in Europe,
Africa, Australia, Asia, and South America).
As the system load demands more active power from the generator, more steam
(or fuel in a combustion turbine) needs to be admitted to the turbine to increase
power output. Hence more energy is transmitted to the generator from the
turbine, in the form of a torque. The higher the power output, the higher the
torque between turbine and generator. The power output of the generator
generally follows the load demand from the system. Therefore the voltages and
currents in the generator are continually changing based on the load demand.
In addition to the normal flux distribution in the main body of the generator,
there are stray fluxes at the extreme ends of the generator that create fringing
flux patterns and induce stray losses in the generator. The stray fluxes must be
accounted for in the overall design.
Generators are made up of two basic members, the stator and the rotor, but the
stator and rotor are each constructed from numerous parts themselves. Rotors
are the high-speed rotating member of the two, and they undergo severe
dynamic mechanical loading as well as the electromagnetic and thermal loads.
The most critical component in the generator are the retaining rings, mounted
on the rotor. The stator is stationary, as the term suggests, but it also sees
significant dynamic forces in terms of vibration and torsional loads, as well as
the electromagnetic, thermal, and high-voltage loading.
The basic function of the generator is to convert mechanical power, delivered
from the shaft of the turbine, into electrical power. Therefore a generator is
actually a rotating mechanical energy converter. The mechanical energy from
the turbine is converted by means of a rotating magnetic field produced by
direct current in the copper winding of the rotor or field, which generates three-
phase alternating currents and voltages in the copper winding of the stator
(armature).
The generators particular to this category are of the two- and four-pole design
employing round-rotors, with rotational operating speeds of 3600 and 1800rpm
in North America, parts of Japan, and Asia (3000 and 1500 rpm in Europe,
Africa, Australia, Asia, and South America).
As the system load demands more active power from the generator, more steam
(or fuel in a combustion turbine) needs to be admitted to the turbine to increase
power output. Hence more energy is transmitted to the generator from the
turbine, in the form of a torque. The higher the power output, the higher the
torque between turbine and generator. The power output of the generator
generally follows the load demand from the system. Therefore the voltages and
currents in the generator are continually changing based on the load demand.
In addition to the normal flux distribution in the main body of the generator,
there are stray fluxes at the extreme ends of the generator that create fringing
flux patterns and induce stray losses in the generator. The stray fluxes must be
accounted for in the overall design.
Generators are made up of two basic members, the stator and the rotor, but the
stator and rotor are each constructed from numerous parts themselves. Rotors
are the high-speed rotating member of the two, and they undergo severe
dynamic mechanical loading as well as the electromagnetic and thermal loads.
The most critical component in the generator are the retaining rings, mounted
on the rotor. The stator is stationary, as the term suggests, but it also sees
significant dynamic forces in terms of vibration and torsional loads, as well as
the electromagnetic, thermal, and high-voltage loading.
STATOR
The stator winding is made up of insulated copper conductor bars that are
distributed around the inside diameter of the stator core, commonly called the
stator bore, in equally spaced slots in the core to ensure symmetrical flux
linkage with the field produced by the rotor. Each slot contains two conductor
bars, one on top of the other. These are generally referred to as top and bottom
bars. Top bars are the ones nearest the slot opening (just under the wedge) and
the bottom bars are the ones at the slot bottom. The core area between slots is
generally called a core tooth. The stator winding is then divided into three
phases, which are almost always wye connected. Wye connection is done to
allow a neural grounding point and for relay protection of the winding. The
three phases are connected to create symmetry between them in the 360 degree
arc of the stator bore. The distribution of the winding is done in such a way as to
produce a 120 degree difference in voltage peaks from one phase to the other,
hence the term ³three-phasevoltage. Each of the three phases may have one or
more parallel circuits within the phas. The stator bars in any particular phase
group are arranged such that there are parallel paths, which overlap between top
and bottom bars. The overlap is staggered between top and bottom bars. The top
bars on one side of the stator bore are connected to the bottom bars on the other
side of the bore in one direction while the bottom bars are connected in the
other direction on the opposite side of the stator. This connection with the bars
on the other side of the stator creates a³reach´ or ³pitch´ of a certain number of
slots. The pitch is therefore the number slots that the stator bars have to reach in
the stator bore arc, separating the two bars to be connected. This is
The stator winding is made up of insulated copper conductor bars that are
distributed around the inside diameter of the stator core, commonly called the
stator bore, in equally spaced slots in the core to ensure symmetrical flux
linkage with the field produced by the rotor. Each slot contains two conductor
bars, one on top of the other. These are generally referred to as top and bottom
bars. Top bars are the ones nearest the slot opening (just under the wedge) and
the bottom bars are the ones at the slot bottom. The core area between slots is
generally called a core tooth. The stator winding is then divided into three
phases, which are almost always wye connected. Wye connection is done to
allow a neural grounding point and for relay protection of the winding. The
three phases are connected to create symmetry between them in the 360 degree
arc of the stator bore. The distribution of the winding is done in such a way as to
produce a 120 degree difference in voltage peaks from one phase to the other,
hence the term ³three-phasevoltage. Each of the three phases may have one or
more parallel circuits within the phas. The stator bars in any particular phase
group are arranged such that there are parallel paths, which overlap between top
and bottom bars. The overlap is staggered between top and bottom bars. The top
bars on one side of the stator bore are connected to the bottom bars on the other
side of the bore in one direction while the bottom bars are connected in the
other direction on the opposite side of the stator. This connection with the bars
on the other side of the stator creates a³reach´ or ³pitch´ of a certain number of
slots. The pitch is therefore the number slots that the stator bars have to reach in
the stator bore arc, separating the two bars to be connected. This is
Figure 4: Stator of turbo generator in NTPC Kawas
Always less than 180 degrees. Once connected, the stator bars form a single coil
or turn. The total width of the overlapping parallels is called the ³breadth.´ the
combination of the pitch and breadth create a ³winding or distribution factor.´
the distribution factor is used to minimize the harmonic content of the generated
voltage. In the case of a two parallel path winding, these may be connected in
series or parallel outside the stator bore, at the termination end of the generator.
ROTOR
The rotor winding is installed in the slots machined in the forging main body
and is distributed symmetrically around the rotor between the poles. The
winding itself is made up of many turns of copper to form the entire series
connected winding. All of the turns associated with a single slot are generally
called a coil. The coils are wound into the winding slots in the forging,
concentrically in corresponding positions on opposite sides of a pole. There are
numerous copper-winding designs employed in generator rotors, but all rotor
windings function basically in the same way. They are configured differently
for different methods of heat removal during operation. In addition almost all
Always less than 180 degrees. Once connected, the stator bars form a single coil
or turn. The total width of the overlapping parallels is called the ³breadth.´ the
combination of the pitch and breadth create a ³winding or distribution factor.´
the distribution factor is used to minimize the harmonic content of the generated
voltage. In the case of a two parallel path winding, these may be connected in
series or parallel outside the stator bore, at the termination end of the generator.
ROTOR
The rotor winding is installed in the slots machined in the forging main body
and is distributed symmetrically around the rotor between the poles. The
winding itself is made up of many turns of copper to form the entire series
connected winding. All of the turns associated with a single slot are generally
called a coil. The coils are wound into the winding slots in the forging,
concentrically in corresponding positions on opposite sides of a pole. There are
numerous copper-winding designs employed in generator rotors, but all rotor
windings function basically in the same way. They are configured differently
for different methods of heat removal during operation. In addition almost all
large turbo generators have directly cooled copper windings by air or hydrogen
cooling gas.
Figure 4: Rotor being installed at the Kawas plant of a turbo generator
Cooling passages are provided within the conductors themselves to eliminate
the temperature drop across the ground insulation and preserve the life of the
insulation material. In a ³axially´ cooled winding, the gas passes through axial
passages in the conductors, being fed from both ends, and exhausted to the air
gap at the axial center of the rotor.
cooling gas.
Figure 4: Rotor being installed at the Kawas plant of a turbo generator
Cooling passages are provided within the conductors themselves to eliminate
the temperature drop across the ground insulation and preserve the life of the
insulation material. In a ³axially´ cooled winding, the gas passes through axial
passages in the conductors, being fed from both ends, and exhausted to the air
gap at the axial center of the rotor.
Stator and rotor slot details
BEARINGS
All turbo generators require bearings to rotate freely with minimal friction and
vibration. The main rotor body must be supported by a bearing at each end of
the generator for this purpose. In some cases where the rotor shaft is very long
at the excitation end of the machine to accommodate the slip/collector rings, a
³steady´ bearing is installed outboard of the slip collector rings. This ensures
that the excitation end of the rotor shaft does not create a wobble that transmits
through the shaft and stimulates excessive vibration in the overall generator
rotor or the turbo generator line. There are generally two common types of
bearings employed in large generators, ³journal´ and ³tilting pad´ bearings.
AUXILIARY SYSTEMS
All large generators require auxiliary systems to handle such things as
lubricating oil for the rotor bearings, hydrogen cooling apparatus, hydrogen
sealing oil, de-mineralized water for stator winding cooling, and excitation
BEARINGS
All turbo generators require bearings to rotate freely with minimal friction and
vibration. The main rotor body must be supported by a bearing at each end of
the generator for this purpose. In some cases where the rotor shaft is very long
at the excitation end of the machine to accommodate the slip/collector rings, a
³steady´ bearing is installed outboard of the slip collector rings. This ensures
that the excitation end of the rotor shaft does not create a wobble that transmits
through the shaft and stimulates excessive vibration in the overall generator
rotor or the turbo generator line. There are generally two common types of
bearings employed in large generators, ³journal´ and ³tilting pad´ bearings.
AUXILIARY SYSTEMS
All large generators require auxiliary systems to handle such things as
lubricating oil for the rotor bearings, hydrogen cooling apparatus, hydrogen
sealing oil, de-mineralized water for stator winding cooling, and excitation
systems for field-current application. Not all generators requireall these systems
and the requirement depends on the size and nature of the machine. For
instance, air cooled turbo generators do not require hydrogen for cooling and
therefore no sealing oil as well. On the other hand, large generators with high
outputs, generally above 400 MVA, have water-cooled stator windings,
hydrogen for cooling the stator core and rotor, seal oil to contain the hydrogen
cooling gas under high pressure, lubricating oil for the bearings, and of course,
an excitation system for field current.
There are five major auxiliary systems that may be used in a generator. They are
given as follows:
1. Lubricating Oil System
2. Hydrogen Cooling System
3. Seal Oil System
4. Stator Cooling Water System
5. Excitation System
1. Lubricating Oil System
The lube-oil system provides oil for all of the turbine and generator bearings as
well as being the source of seal oil for the seal-oil system. The lube-oil system
is generally grouped in with the turbine components and is not usually looked
after by the generator side during maintenance.
The main components of the lube-oil system consists generally of the main
lube-oil tank, pumps, heat exchangers, filters and strainers, centrifuge or
purifier, vapor extractor, and various check valves and instrumentation. The
and the requirement depends on the size and nature of the machine. For
instance, air cooled turbo generators do not require hydrogen for cooling and
therefore no sealing oil as well. On the other hand, large generators with high
outputs, generally above 400 MVA, have water-cooled stator windings,
hydrogen for cooling the stator core and rotor, seal oil to contain the hydrogen
cooling gas under high pressure, lubricating oil for the bearings, and of course,
an excitation system for field current.
There are five major auxiliary systems that may be used in a generator. They are
given as follows:
1. Lubricating Oil System
2. Hydrogen Cooling System
3. Seal Oil System
4. Stator Cooling Water System
5. Excitation System
1. Lubricating Oil System
The lube-oil system provides oil for all of the turbine and generator bearings as
well as being the source of seal oil for the seal-oil system. The lube-oil system
is generally grouped in with the turbine components and is not usually looked
after by the generator side during maintenance.
The main components of the lube-oil system consists generally of the main
lube-oil tank, pumps, heat exchangers, filters and strainers, centrifuge or
purifier, vapor extractor, and various check valves and instrumentation. The
main oil tank serves both the turbine and generator bearing and is often also the
source of the sealing oil for the hydrogen seals. It is usually located under the
turbines and holds thousands of gallons of oil. Heat exchangers are provided for
heat removal from the lube oil. Raw water from the local lake or river is
circulated on one side of the cooler to remove the heat from the lube oil
circulating on the other side of the heat exchanger. Full flow filters and/or
strainers, or a combination of both, are employed for removal of debris from the
lube oil. Strainers are generally sized to remove larger debris and filters for
debris in the range of a few microns and larger. They can be mechanical or
organic type filters and strainers. Debris removal is important to reduce the
possibility of scoring the bearing Babbitt or plugging of the oil lines. A
centrifuge or purifier is used to remove moisture from the oil. Moisture is also a
contaminant to oil and can cause it to lose its lubricating properties.
2. Hydrogen Cooling System
As the hydrogen cooling gas picks up heat from the various generator
components within the machine, its temperature rises significantly. This can be
as much as 46oC, and therefore the hydrogen must be cooled down prior to
being re-circulated through the machine for continuous cooling. Hydrogen
coolers or heat exchangers are employed for this purpose. Hydrogen coolers are
basically heat exchangers mounted inside the generator in the enclosed
atmosphere. Cooling tubes with “fins” are used to enlarge the surface area for
cooling, as the hydrogen gas passes over the outside of the finned tubes. “Raw
water” (filtered and treated) from the local river or lake is pumped through the
tubes to take the heat away from the hydrogen gas and outside the generator.
The tubes must be extremely leak-tight to ensure that hydrogen gas does not
enter into the tubes, since the gas is at a higher pressure than the raw water.
3. Seal Oil System
As most large generators use hydrogen under high pressure for cooling the
various internal components. To keep the hydrogen inside the generator, various
places in the generator are required to seal against hydrogen leakage to
atmosphere. One of the most difficult seals made is the juncture between the
stator and the rotating shaft of the rotor. This is done by a set of hydrogen seals
at both ends of the machine. The seals may be of the journal (ring) type or the
thrust-collar type. But one thing both arrangements have in common is the
requirement of high- pressure oil into the seal to make the actual “seal.” The
system, which provides the oil to do this, is called the seal-oil system. In
general, the most common type of seal is the journal type. This arrangement
functions by pressurized oil fed between two floating segmented rings, usually
made of bronze or Babbitt steel. At the ring outlet, against the shaft, oil flows in
source of the sealing oil for the hydrogen seals. It is usually located under the
turbines and holds thousands of gallons of oil. Heat exchangers are provided for
heat removal from the lube oil. Raw water from the local lake or river is
circulated on one side of the cooler to remove the heat from the lube oil
circulating on the other side of the heat exchanger. Full flow filters and/or
strainers, or a combination of both, are employed for removal of debris from the
lube oil. Strainers are generally sized to remove larger debris and filters for
debris in the range of a few microns and larger. They can be mechanical or
organic type filters and strainers. Debris removal is important to reduce the
possibility of scoring the bearing Babbitt or plugging of the oil lines. A
centrifuge or purifier is used to remove moisture from the oil. Moisture is also a
contaminant to oil and can cause it to lose its lubricating properties.
2. Hydrogen Cooling System
As the hydrogen cooling gas picks up heat from the various generator
components within the machine, its temperature rises significantly. This can be
as much as 46oC, and therefore the hydrogen must be cooled down prior to
being re-circulated through the machine for continuous cooling. Hydrogen
coolers or heat exchangers are employed for this purpose. Hydrogen coolers are
basically heat exchangers mounted inside the generator in the enclosed
atmosphere. Cooling tubes with “fins” are used to enlarge the surface area for
cooling, as the hydrogen gas passes over the outside of the finned tubes. “Raw
water” (filtered and treated) from the local river or lake is pumped through the
tubes to take the heat away from the hydrogen gas and outside the generator.
The tubes must be extremely leak-tight to ensure that hydrogen gas does not
enter into the tubes, since the gas is at a higher pressure than the raw water.
3. Seal Oil System
As most large generators use hydrogen under high pressure for cooling the
various internal components. To keep the hydrogen inside the generator, various
places in the generator are required to seal against hydrogen leakage to
atmosphere. One of the most difficult seals made is the juncture between the
stator and the rotating shaft of the rotor. This is done by a set of hydrogen seals
at both ends of the machine. The seals may be of the journal (ring) type or the
thrust-collar type. But one thing both arrangements have in common is the
requirement of high- pressure oil into the seal to make the actual “seal.” The
system, which provides the oil to do this, is called the seal-oil system. In
general, the most common type of seal is the journal type. This arrangement
functions by pressurized oil fed between two floating segmented rings, usually
made of bronze or Babbitt steel. At the ring outlet, against the shaft, oil flows in
both directions from the seals along the rotating shaft. For the thrust-collar type,
the oil is fed into a Babbitt running face via oil delivery ports, and makes the
seal against the rotating thrust collar. Again, the oil flows in two directions, to
the air side and the hydrogen side of the seals. The seal oil itself is actually a
portion of the lube oil, diverted from the lubricating oil system. It is then fed to
a separate system of its own with pumps, motors, hydrogen detraining or
vacuum degassing equipment, and controls to regulate the pressure and flow.
Fig. Seal oil system-package unit
The seal-oil pressure at the hydrogen seals is maintained generally about 15 psi
above the hydrogen pressure to stop hydrogen from leaking past the seals. The
differential pressure is maintained by a controller to ensure continuous and
positive sealing at all times when there is hydrogen in the generator. One of the
critical components of the seal oil system is the hydrogen degasifying plant. The
most common method of removing entrained hydrogen and other gases is to
vacuum-treat the seal oil before supplying it to the seals. This is generally done
the oil is fed into a Babbitt running face via oil delivery ports, and makes the
seal against the rotating thrust collar. Again, the oil flows in two directions, to
the air side and the hydrogen side of the seals. The seal oil itself is actually a
portion of the lube oil, diverted from the lubricating oil system. It is then fed to
a separate system of its own with pumps, motors, hydrogen detraining or
vacuum degassing equipment, and controls to regulate the pressure and flow.
Fig. Seal oil system-package unit
The seal-oil pressure at the hydrogen seals is maintained generally about 15 psi
above the hydrogen pressure to stop hydrogen from leaking past the seals. The
differential pressure is maintained by a controller to ensure continuous and
positive sealing at all times when there is hydrogen in the generator. One of the
critical components of the seal oil system is the hydrogen degasifying plant. The
most common method of removing entrained hydrogen and other gases is to
vacuum-treat the seal oil before supplying it to the seals. This is generally done
in the main seal oil supply tank. As the oil is pulled into the storage tank under
vacuum, through a spray nozzle, the seal oil is broken up into a fine spray. This
allows the removal of dissolved gases. In addition there is often a re-circulating
pump to re-circulate oil back to the tank through a series of spray nozzles for
continuous gas removal. After passing through the generator shaft seals, the oil
goes through the detraining sections before it returns to the bearing oil drain. As
a safety feature there is often a dc motor driven emergency seal-oil pump
provided. This motor will start automatically on loss of oil pressure from the
main seal-oil pump. This is to ensure that the generator can be shut down safely
without risk to personnel or the equipment.
4. Stator Cooling Water System
The stator cooling water system (SCW) is used to provide a source of de-
mineralized water to the generator stator winding for direct cooling of the stator
winding and associated components.SCW is generally used in machines rated at
or above 300 MVA. Most SCW systems are provided as package units,
mounted on a singular platform, which includes all of the SCW system
components. All components of the system are generally made from stainless
steel or copper materials.
vacuum, through a spray nozzle, the seal oil is broken up into a fine spray. This
allows the removal of dissolved gases. In addition there is often a re-circulating
pump to re-circulate oil back to the tank through a series of spray nozzles for
continuous gas removal. After passing through the generator shaft seals, the oil
goes through the detraining sections before it returns to the bearing oil drain. As
a safety feature there is often a dc motor driven emergency seal-oil pump
provided. This motor will start automatically on loss of oil pressure from the
main seal-oil pump. This is to ensure that the generator can be shut down safely
without risk to personnel or the equipment.
4. Stator Cooling Water System
The stator cooling water system (SCW) is used to provide a source of de-
mineralized water to the generator stator winding for direct cooling of the stator
winding and associated components.SCW is generally used in machines rated at
or above 300 MVA. Most SCW systems are provided as package units,
mounted on a singular platform, which includes all of the SCW system
components. All components of the system are generally made from stainless
steel or copper materials.
5. Excitation System
Rotating commutator exciters as a source of DC power for the AC generator
field generally have been replaced by silicon diode power rectifier systems of
the static or brushless type.
• A typical brushless system includes a rotating permanent magnet pilot exciter
with the stator connected through the excitation switchgear to the stationary
field of an AC exciter with rotating armature and a rotating silicon diode
rectifier assembly, which in turn is connected to the rotating field of the
generator. This arrangement eliminates both the commutator and the collector
rings. Also, part of the system is a solid state automatic voltage regulator, a
means of manual voltage regulation, and necessary control devices for
mounting on a remote panel. The exciter rotating parts and the diodes are
mounted on the generator shaft; viewing during operation must utilize a strobe
light.
• A typical static system includes a three-phase excitation potential transformer,
three single- phase current transformers, an excitation cubicle with field breaker
and discharge resistor, one automatic and one manual static thyristor type
voltage regulators, a full wave static rectifier, necessary devices for mounting
on a remote panel, and a collector assembly for connection to the generator
field.
Exciter stator
Rotating commutator exciters as a source of DC power for the AC generator
field generally have been replaced by silicon diode power rectifier systems of
the static or brushless type.
• A typical brushless system includes a rotating permanent magnet pilot exciter
with the stator connected through the excitation switchgear to the stationary
field of an AC exciter with rotating armature and a rotating silicon diode
rectifier assembly, which in turn is connected to the rotating field of the
generator. This arrangement eliminates both the commutator and the collector
rings. Also, part of the system is a solid state automatic voltage regulator, a
means of manual voltage regulation, and necessary control devices for
mounting on a remote panel. The exciter rotating parts and the diodes are
mounted on the generator shaft; viewing during operation must utilize a strobe
light.
• A typical static system includes a three-phase excitation potential transformer,
three single- phase current transformers, an excitation cubicle with field breaker
and discharge resistor, one automatic and one manual static thyristor type
voltage regulators, a full wave static rectifier, necessary devices for mounting
on a remote panel, and a collector assembly for connection to the generator
field.
Exciter stator
Exciter rotor
Specifications
• Static, brushless with rotating diodes on rotor.
• Shunt excitation with 11.5 kV excitation transformer
• Excitation transformer directly connected on generator busbars.
• Voltage regulation done using thyristors.
• 125 Volts DC for field flashing and boosting.
• The main exciter is directly mounted on the generator shaft.
• The exciter has field coils on the stator and armature on the rotor
Specifications
• Static, brushless with rotating diodes on rotor.
• Shunt excitation with 11.5 kV excitation transformer
• Excitation transformer directly connected on generator busbars.
• Voltage regulation done using thyristors.
• 125 Volts DC for field flashing and boosting.
• The main exciter is directly mounted on the generator shaft.
• The exciter has field coils on the stator and armature on the rotor
Single line diagram and picture of exciter
Cross section view of exciter
BOILERS:-
boiler is a closed vessel in which fluid (generally water) is heated. The fluid
does not necessarily boil. The heated or vaporized fluid exits the boiler for use
in various processes or heating applications including water heating, central
heating, boiler-based power generation, cooking, and sanitation.
A boiler is defined as “A closed vessel in which water or other liquid is heated,
steam or vapour is generated, steam is superheated, or any combination thereof,
under pressure or vacuum, for use external to itself, by the direct application of
energy from the combustion of fuels, from electricity or nuclear energy ”.
A boiler is the main working component of thermal power plants
Fuel Used in Boilers
Boiler Furnaces compatible with
Solid fuels:
Wood
Coal
Briquettes
Pet Coke
Rice Husk
Liquid Fuels:
LDO
Furnace oil
Gaseous Fuels:
LPG
LNG
PNG can be used to carry out the combustion for the specific purpose.
Components of a Boiler Systems
There are 3 backbone components of any boilers system:
boiler is a closed vessel in which fluid (generally water) is heated. The fluid
does not necessarily boil. The heated or vaporized fluid exits the boiler for use
in various processes or heating applications including water heating, central
heating, boiler-based power generation, cooking, and sanitation.
A boiler is defined as “A closed vessel in which water or other liquid is heated,
steam or vapour is generated, steam is superheated, or any combination thereof,
under pressure or vacuum, for use external to itself, by the direct application of
energy from the combustion of fuels, from electricity or nuclear energy ”.
A boiler is the main working component of thermal power plants
Fuel Used in Boilers
Boiler Furnaces compatible with
Solid fuels:
Wood
Coal
Briquettes
Pet Coke
Rice Husk
Liquid Fuels:
LDO
Furnace oil
Gaseous Fuels:
LPG
LNG
PNG can be used to carry out the combustion for the specific purpose.
Components of a Boiler Systems
There are 3 backbone components of any boilers system:
1. Boiler Feed Water System
Water that converts into steam by steam boilers system called Feed water &
system that regulates feed water called Feed water system.
There are two types of feed water systems in boilers:
Open feed System
Closed feed system
There are two main sources of feed water:
Condensed steam returned from the processes
Raw water arranged from outside the boilers plant processes ( Called:
Makeup Water)
2. Boiler Steam System
Steam System is kind of main controlling system of boilers process. Steam
Systems are responsible to collect & control all generated steam in the process.
Steam systems send steam generated in the process to the point of use through
pipes ( piping system). Throughout the process, steam pressure is controlled and
regulated with the help of boilers system parts such as valves, steam pressure
gauges etc.
3. Boilers Fuel System
Fueling is the heart of boilers process & fuel system consists of all the necessary
components and equipment to feed fuel to generate the required heat. The
equipment required in the fuel system depends on the type of fuel used in the
system.
Boiler Applications
The Boilers have a very a wide application in different industries such as
Power Sector
Textiles
Plywood
Food Processing Industry
FMCG
Sugar Plants
Thermal Power Plants
Water that converts into steam by steam boilers system called Feed water &
system that regulates feed water called Feed water system.
There are two types of feed water systems in boilers:
Open feed System
Closed feed system
There are two main sources of feed water:
Condensed steam returned from the processes
Raw water arranged from outside the boilers plant processes ( Called:
Makeup Water)
2. Boiler Steam System
Steam System is kind of main controlling system of boilers process. Steam
Systems are responsible to collect & control all generated steam in the process.
Steam systems send steam generated in the process to the point of use through
pipes ( piping system). Throughout the process, steam pressure is controlled and
regulated with the help of boilers system parts such as valves, steam pressure
gauges etc.
3. Boilers Fuel System
Fueling is the heart of boilers process & fuel system consists of all the necessary
components and equipment to feed fuel to generate the required heat. The
equipment required in the fuel system depends on the type of fuel used in the
system.
Boiler Applications
The Boilers have a very a wide application in different industries such as
Power Sector
Textiles
Plywood
Food Processing Industry
FMCG
Sugar Plants
Thermal Power Plants
WATER SYSTEMS: -
Raw water supply system
The raw water is supplied to the raw water tank. The raw water is clarified in
the pretreatment plant and is stored in a clarified water tank to be used as
circulating water make up and for compressor cooling.
Water Treatment Plant
The clarified water is filtered in two pressure filters to feed de-mineralized
water plant and to be used for potable water system, for HVAC make up and for
service water. An ion exchange water treatment plant with two streams of 100%
capacity each producing, de-mineralized water for the facility. 100% capacity is
defined as normal water steam cycle losses plus up to 25% loss of process steam
condensate. Limited time periods with higher demand for demineralized water
can be covered by water stored in two demineralized water tanks.
DM Water Supply
Demineralization Plant supply DM water to Boiler, Generator cooling etc. DM
water is pumped by five DM water pumps to the WSCS, the NOx high pressure
pump blocks at the gas turbines and the other occasional consumers like dosing
and sampling station, closed cooling water systems and GT compressor washing
skid. One pump will always be in stand-by to fulfill the supply demands at any
time.
Potable Water Supply
Potable water is taken from the filtered clarified water supply and distributed
within the power plant area via a pipe network.
Cooling Water System
A natural draught wet cooling tower system transposes the waste heat of the
water steam cycle to the atmosphere. Two 100% main cooling water pumps
supply the cold water from the cold-water basin to the main condensers and the
intercoolers of the CCW system. The condenser tubes in clean conditions.
Losses in the system are made up by clarified raw water. The cooling water
quality is controlled by the cooling water sampling water sampling and dosing
station, where chemicals can be dosed.
Raw water supply system
The raw water is supplied to the raw water tank. The raw water is clarified in
the pretreatment plant and is stored in a clarified water tank to be used as
circulating water make up and for compressor cooling.
Water Treatment Plant
The clarified water is filtered in two pressure filters to feed de-mineralized
water plant and to be used for potable water system, for HVAC make up and for
service water. An ion exchange water treatment plant with two streams of 100%
capacity each producing, de-mineralized water for the facility. 100% capacity is
defined as normal water steam cycle losses plus up to 25% loss of process steam
condensate. Limited time periods with higher demand for demineralized water
can be covered by water stored in two demineralized water tanks.
DM Water Supply
Demineralization Plant supply DM water to Boiler, Generator cooling etc. DM
water is pumped by five DM water pumps to the WSCS, the NOx high pressure
pump blocks at the gas turbines and the other occasional consumers like dosing
and sampling station, closed cooling water systems and GT compressor washing
skid. One pump will always be in stand-by to fulfill the supply demands at any
time.
Potable Water Supply
Potable water is taken from the filtered clarified water supply and distributed
within the power plant area via a pipe network.
Cooling Water System
A natural draught wet cooling tower system transposes the waste heat of the
water steam cycle to the atmosphere. Two 100% main cooling water pumps
supply the cold water from the cold-water basin to the main condensers and the
intercoolers of the CCW system. The condenser tubes in clean conditions.
Losses in the system are made up by clarified raw water. The cooling water
quality is controlled by the cooling water sampling water sampling and dosing
station, where chemicals can be dosed.
Closed Cooling Water System
A separate closed cooling water system for each unit ensures the cooling of the
lube oil system, the HP feed water pumps, the LP boiler preheated circulating
pumps, the generator air coolers, the sampling system, etc.
The heat is dissipated to the main cooling water system via 100% capacity
water-to-water heat exchanger. Losses in the system are made up by DM water.
COOLING TOWER
Cooling Towers have one function: -
Remove heat from the water discharged from the condenser so that the water
can be discharged to the river or re circulated and reused.
Some power plants, usually located on lakes or rivers, use cooling towers as a
method of cooling the circulating water (the third non-radioactive cycle) that
has been heated in the condenser. During colder months and fish non-spawning
periods, the discharge from the condenser may be directed to the river.
Recirculation of the water back to the inlet to the condenser occurs during
certain fish sensitive times of the year (e.g. spring, summer, and fall) so that
only a limited amount of water from the plant condenser may be discharged to
the lake or river. It is important to note that the heat transferred in a condenser
may heat the circulating water as much as 40 degrees Fahrenheit (F). In some
cases, power plants may have restrictions that prevent discharging water to the
river at more than 90 degrees f. In other cases, they may have limits of no more
than 5 degrees f difference between intake and discharge (averaged over a 24
hour period). When Cooling Towers are used, plant efficiency usually drops.
One reason is that the Cooling Tower pumps (and fans, if used) consume a
lot of power.
A separate closed cooling water system for each unit ensures the cooling of the
lube oil system, the HP feed water pumps, the LP boiler preheated circulating
pumps, the generator air coolers, the sampling system, etc.
The heat is dissipated to the main cooling water system via 100% capacity
water-to-water heat exchanger. Losses in the system are made up by DM water.
COOLING TOWER
Cooling Towers have one function: -
Remove heat from the water discharged from the condenser so that the water
can be discharged to the river or re circulated and reused.
Some power plants, usually located on lakes or rivers, use cooling towers as a
method of cooling the circulating water (the third non-radioactive cycle) that
has been heated in the condenser. During colder months and fish non-spawning
periods, the discharge from the condenser may be directed to the river.
Recirculation of the water back to the inlet to the condenser occurs during
certain fish sensitive times of the year (e.g. spring, summer, and fall) so that
only a limited amount of water from the plant condenser may be discharged to
the lake or river. It is important to note that the heat transferred in a condenser
may heat the circulating water as much as 40 degrees Fahrenheit (F). In some
cases, power plants may have restrictions that prevent discharging water to the
river at more than 90 degrees f. In other cases, they may have limits of no more
than 5 degrees f difference between intake and discharge (averaged over a 24
hour period). When Cooling Towers are used, plant efficiency usually drops.
One reason is that the Cooling Tower pumps (and fans, if used) consume a
lot of power.
Major Components:
Cooling Tower (Supply) Basin
Water is supplied from the discharge of the Circulating Water System to a
Distribution Basin, from which the Cooling Tower Pumps take suction.
Cooling Tower Pumps
These large pumps supply water at over 100,000 gallons per minute to one or
more Cooling Towers. Each pump is usually over 15 feet deep. The motor
assembly may be 8 to 10 feet high. The total electrical demand of all the
Cooling Tower pumps may be as much as 5% of the electrical output of the
station.
Cooling Towers
Natural Draft Cooling Tower
The green flow paths show how the warm water leaves the plant proper, is
pumped to the natural draft cooling tower and is distributed. The cooled water,
including makeup from the lake to account for evaporation losses to the
atmosphere, is returned to the condenser.
Cooling Tower (Supply) Basin
Water is supplied from the discharge of the Circulating Water System to a
Distribution Basin, from which the Cooling Tower Pumps take suction.
Cooling Tower Pumps
These large pumps supply water at over 100,000 gallons per minute to one or
more Cooling Towers. Each pump is usually over 15 feet deep. The motor
assembly may be 8 to 10 feet high. The total electrical demand of all the
Cooling Tower pumps may be as much as 5% of the electrical output of the
station.
Cooling Towers
Natural Draft Cooling Tower
The green flow paths show how the warm water leaves the plant proper, is
pumped to the natural draft cooling tower and is distributed. The cooled water,
including makeup from the lake to account for evaporation losses to the
atmosphere, is returned to the condenser.
Figure 10: cooling tower schematic
220 kV SWITCH YARD
The Switchyard is a junction connecting the Transmission and distribution
system to the power plant. As we know that electrical energy can’t be stored
like cells, so what we generate should be consumed instantaneously. But as the
load is not constants therefore we generate electricity according to need i.e. the
generation depends upon load. The yard is the places from where the electricity
is send outside. It has both outdoor and indoor equipment’s.
OUTDOOR EQUIPMENTS :
i. BUS BAR.
ii. TRANSFER BUS
iii. LIGHTENING ARRESTER
iv. BREAKER
v. ISOLATOR
vi. INSULATORS
vii. CAPACITATIVE VOLTAGE TRANSFORMER
viii. EARTHING ROD
ix. CURRENT TRANSFORMER.
x. POTENTIAL TRANSFORMER
xi. CAPACITOR BANK
INDOOR EQUIPMENTS :
i. RELAYS.
ii. CONTROL PANELS
iii. CIRCUIT BREAKERS
The Switchyard is a junction connecting the Transmission and distribution
system to the power plant. As we know that electrical energy can’t be stored
like cells, so what we generate should be consumed instantaneously. But as the
load is not constants therefore we generate electricity according to need i.e. the
generation depends upon load. The yard is the places from where the electricity
is send outside. It has both outdoor and indoor equipment’s.
OUTDOOR EQUIPMENTS :
i. BUS BAR.
ii. TRANSFER BUS
iii. LIGHTENING ARRESTER
iv. BREAKER
v. ISOLATOR
vi. INSULATORS
vii. CAPACITATIVE VOLTAGE TRANSFORMER
viii. EARTHING ROD
ix. CURRENT TRANSFORMER.
x. POTENTIAL TRANSFORMER
xi. CAPACITOR BANK
INDOOR EQUIPMENTS :
i. RELAYS.
ii. CONTROL PANELS
iii. CIRCUIT BREAKERS
BUS BAR
Bus bars generally are of high conductive aluminium conforming to IS-5082 or
copper of adequate cross section .Bus bar located in air insulated enclosures &
segregated from all other components .Bus bar is preferably cover with
polyurethane. The conductor carrying current and having multiple numbers of
incoming and outgoing line connections can be called as bus bar, which is
commonly used in substations. These are classified into different types like
single bus, double bus and ring bus.
There are two bus bar in NTPC plant which named as bus 1 & bus 2
TRANSFER BUS
This bus is a backup bus which comes handy when any of the buses become
faulty. When any operation bus has fault, this bus is brought into circuit and
then faulty line is removed there by restoring healthy power line.
It connected at a time single line or one GT bay or ST bay.
LIGHTENING ARRESTOR
It saves the transformer and reactor from over voltage and over currents. It
grounds the overload if there is fault on the line and it prevents the generator
transformer. The practice is to install lightening arrestor at the incoming
terminal of the line. We have to use the lightning arrester both in primary and
secondary of transformer and in reactors. A meter is provided which indicates
the surface leakage and internal grading current of arrester.
BREAKER
It is a on load Device .Circuit breaker is an arrangement by which we can break
the circuit or flow of current. A circuit breaker in station serves the same
purpose as switch but it has many added and complex features. The basic
construction of any circuit breaker requires the separation of contact in an
insulating fluid that servers two functions:
i. Extinguishes the arc drawn between the contacts when circuit breaker
opens.
Bus bars generally are of high conductive aluminium conforming to IS-5082 or
copper of adequate cross section .Bus bar located in air insulated enclosures &
segregated from all other components .Bus bar is preferably cover with
polyurethane. The conductor carrying current and having multiple numbers of
incoming and outgoing line connections can be called as bus bar, which is
commonly used in substations. These are classified into different types like
single bus, double bus and ring bus.
There are two bus bar in NTPC plant which named as bus 1 & bus 2
TRANSFER BUS
This bus is a backup bus which comes handy when any of the buses become
faulty. When any operation bus has fault, this bus is brought into circuit and
then faulty line is removed there by restoring healthy power line.
It connected at a time single line or one GT bay or ST bay.
LIGHTENING ARRESTOR
It saves the transformer and reactor from over voltage and over currents. It
grounds the overload if there is fault on the line and it prevents the generator
transformer. The practice is to install lightening arrestor at the incoming
terminal of the line. We have to use the lightning arrester both in primary and
secondary of transformer and in reactors. A meter is provided which indicates
the surface leakage and internal grading current of arrester.
BREAKER
It is a on load Device .Circuit breaker is an arrangement by which we can break
the circuit or flow of current. A circuit breaker in station serves the same
purpose as switch but it has many added and complex features. The basic
construction of any circuit breaker requires the separation of contact in an
insulating fluid that servers two functions:
i. Extinguishes the arc drawn between the contacts when circuit breaker
opens.
ii. It provides adequate insulation between the contacts and from each
contact to earth
Types Of Breakers:-
Circuit breaker types are classified according to many different criteria such as
Applicable Voltage
Location where it is installed
External design characteristic
Medium used for the interruption (most popular types)
Circuit breaker types based on voltage
The circuit breakers based on voltage are classified in to groups.
1. Low voltage circuit breakers:
The breakers which are rated for use at low voltages up to 2kV are called low
voltage circuit breakers. These are mostly used in small scale industries.
2. High Voltage circuit breakers:
The breakers which are rated for use at voltages greater than 2KV are called as
high voltage circuit breakers. High voltage circuit breakers are further
subdivided in to transmission class breakers which are rated 123KV and above
and distribution or medium voltage class (lesser than 72KV) circuit breakers.
(g) Circuit breaker types by installation location:
Based on their location of installation circuit breakers are classified as indoor
circuit breakers and outdoor circuit breakers.
contact to earth
Types Of Breakers:-
Circuit breaker types are classified according to many different criteria such as
Applicable Voltage
Location where it is installed
External design characteristic
Medium used for the interruption (most popular types)
Circuit breaker types based on voltage
The circuit breakers based on voltage are classified in to groups.
1. Low voltage circuit breakers:
The breakers which are rated for use at low voltages up to 2kV are called low
voltage circuit breakers. These are mostly used in small scale industries.
2. High Voltage circuit breakers:
The breakers which are rated for use at voltages greater than 2KV are called as
high voltage circuit breakers. High voltage circuit breakers are further
subdivided in to transmission class breakers which are rated 123KV and above
and distribution or medium voltage class (lesser than 72KV) circuit breakers.
(g) Circuit breaker types by installation location:
Based on their location of installation circuit breakers are classified as indoor
circuit breakers and outdoor circuit breakers.
(i) Indoor circuit breakers:
indoor electrical circuit breaker
These breakers are designed for use only inside buildings or weather resistant
enclosures. Generally indoor circuit breakers are operated at medium voltage
with a metal cad switchgear enclosure.
(ii) Out Door Circuit breakers:
Outdoor circuit breakers
These breakers are designed to use at outside without any roof. So these
breakers external enclosure arrangement will be strong compared to indoor
breakers to with stand wear and tear.
In conclusion the only difference between indoor and outdoor circuit breakers is
the external structural packaging or the enclosures that are used. Besides that all
other parts like circuit interrupting mechanisms will be the same for the same
operating voltage
.
indoor electrical circuit breaker
These breakers are designed for use only inside buildings or weather resistant
enclosures. Generally indoor circuit breakers are operated at medium voltage
with a metal cad switchgear enclosure.
(ii) Out Door Circuit breakers:
Outdoor circuit breakers
These breakers are designed to use at outside without any roof. So these
breakers external enclosure arrangement will be strong compared to indoor
breakers to with stand wear and tear.
In conclusion the only difference between indoor and outdoor circuit breakers is
the external structural packaging or the enclosures that are used. Besides that all
other parts like circuit interrupting mechanisms will be the same for the same
operating voltage
.
Circuit Breaker types based on External design:
Based on their structural design the circuit breakers are classified as dead tank
circuit breakers and live tank circuit breakers.
(iii)
(iv) Dead Tank Circuit breakers:
Dead tank circuit breaker
A breaker which has its enclosed tank at ground potential is called as dead tank
circuit breakers. The tank encloses all the interrupting and insulating medium.
In simple it can be said that the tank is shorted to ground or it is at dead
potential. Dead tank circuit breakers are preferred choice in US.
1) Advantages of Dead tank breakers over live tank breakers:
Multiple current transformers can be installed at both, the line side and
load side of the breaker.
This construction offers higher seismic withstand capability because it is
almost near to the ground.
Easy installation and factory made adjustments.
Based on their structural design the circuit breakers are classified as dead tank
circuit breakers and live tank circuit breakers.
(iii)
(iv) Dead Tank Circuit breakers:
Dead tank circuit breaker
A breaker which has its enclosed tank at ground potential is called as dead tank
circuit breakers. The tank encloses all the interrupting and insulating medium.
In simple it can be said that the tank is shorted to ground or it is at dead
potential. Dead tank circuit breakers are preferred choice in US.
1) Advantages of Dead tank breakers over live tank breakers:
Multiple current transformers can be installed at both, the line side and
load side of the breaker.
This construction offers higher seismic withstand capability because it is
almost near to the ground.
Easy installation and factory made adjustments.
(v) Live tank circuit breakers:
live tank circuit breaker
A Breaker which has its tank housing the interrupter is at potential above the
ground is called as live tank circuit breaker. As the name specifies it is above
the ground with some insulation medium in between.
1) Advantages of Live tank circuit breakers:
Cost of the circuit breaker is less
Less mounting space is required
Use a lesser amount of interrupting medium.
Circuit breaker type by interrupting mechanism:
This is main class of circuit breaker types. According to the arc interrupting and
insulating medium that is used the circuit breakers classified as follows:
Air Circuit breaker:
This uses air as interrupting and insulating medium. These are further classified
as Air magnetic circuit breakers and Air blast circuit breakers.
Oil circuit breaker:
This uses oil as interrupting and insulating medium. The oil circuit breakers are
divided in two types based on the pressure and amount of oil used as Bulk oil
circuit breaker and minimum oil circuit breakers.
These two types are older circuit breakers. In recent years in addition to the
above two, two more interrupting mediums are introduced.
live tank circuit breaker
A Breaker which has its tank housing the interrupter is at potential above the
ground is called as live tank circuit breaker. As the name specifies it is above
the ground with some insulation medium in between.
1) Advantages of Live tank circuit breakers:
Cost of the circuit breaker is less
Less mounting space is required
Use a lesser amount of interrupting medium.
Circuit breaker type by interrupting mechanism:
This is main class of circuit breaker types. According to the arc interrupting and
insulating medium that is used the circuit breakers classified as follows:
Air Circuit breaker:
This uses air as interrupting and insulating medium. These are further classified
as Air magnetic circuit breakers and Air blast circuit breakers.
Oil circuit breaker:
This uses oil as interrupting and insulating medium. The oil circuit breakers are
divided in two types based on the pressure and amount of oil used as Bulk oil
circuit breaker and minimum oil circuit breakers.
These two types are older circuit breakers. In recent years in addition to the
above two, two more interrupting mediums are introduced.
Vacuum circuit breakers:
This uses vacuum as the interrupting medium because of its high dielectric and
diffusive properties as interrupting medium.12 kV VCB is using in NTPC.
SF6 Circuit breakers:
SF6 has 100 times high dielectric strength than air and oil as interrupting
medium. The breaker with SF6 interrupting medium is called as SF6 circuit
breaker
.
Other types of circuit breakers:
The following are some other types of circuit breakers.
MCB (Miniature circuit breaker):
These current ratings are less than 100A with only one over current protection
in built within it. The trip settings are not adjustable in MCB.
MCCB (Moulded case circuit breakers):
These current ratings are higher at 1000A. This has earth fault protection in
addition to over current protection. The trip settings of the breaker can vary
easily.
Single pole circuit breaker:
It has one hot wire and one neutral wire operated at 120V. on fault it interrupts
only one hot wire.
Double pole circuit breaker:
In case of 220 V there are two hot wires, so two poles are needed to interrupt
the two hot wires on fault. Double pole circuit breaker is used in this case to
interrupt the two hot wires.
GFI or GFCI circuit breaker (Ground fault interrupter):
These are safety switches which trips on ground fault current. In brief this
breaker interrupts the electrical circuit when a variance is detected between
phase and neutral wires.
This uses vacuum as the interrupting medium because of its high dielectric and
diffusive properties as interrupting medium.12 kV VCB is using in NTPC.
SF6 Circuit breakers:
SF6 has 100 times high dielectric strength than air and oil as interrupting
medium. The breaker with SF6 interrupting medium is called as SF6 circuit
breaker
.
Other types of circuit breakers:
The following are some other types of circuit breakers.
MCB (Miniature circuit breaker):
These current ratings are less than 100A with only one over current protection
in built within it. The trip settings are not adjustable in MCB.
MCCB (Moulded case circuit breakers):
These current ratings are higher at 1000A. This has earth fault protection in
addition to over current protection. The trip settings of the breaker can vary
easily.
Single pole circuit breaker:
It has one hot wire and one neutral wire operated at 120V. on fault it interrupts
only one hot wire.
Double pole circuit breaker:
In case of 220 V there are two hot wires, so two poles are needed to interrupt
the two hot wires on fault. Double pole circuit breaker is used in this case to
interrupt the two hot wires.
GFI or GFCI circuit breaker (Ground fault interrupter):
These are safety switches which trips on ground fault current. In brief this
breaker interrupts the electrical circuit when a variance is detected between
phase and neutral wires.
Arc Fault circuit interrupter (AFCI):
It interrupts the circuit during excessive arc conditions and prevents fire. Under
normal arcing condition this will idle and does not interrupt the circuit.
SF6 circuit breakers are used in switchyard of NTPC kawas. .These breakers are
fixed , hydraulic oil operated breakers. Sulphur hexa fluoride circuit breaprotect
electrical power station and distribution systems by using interrupting electric
current , when tripped by a protective relay.
Instead of oil , air or a vacuum circuit breakers ,SF6 circuit breakers used
because it uses SF6 gas to quench the arc on opening a circuit.SF6 has excellent
dielectric, arc quenching, chemical and other physical properties.SF6 is a spark
reduces agent.
It is used for voltage range of upto 800 kV .
Specification Of SF6 Breakers:-
SF6 Breaker Name Plate - GEC ALSTHOM( France Made)
Voltage=245 kV Type= Fx22 F =50 Hz
Normal Current =2500 A Total mass of SF6 gas=29.5 kg
Total Mass of Circuit Breakers = 6030 kg
SF6 gas Pressure at 20
o
C ,1013 hPa = 7.65 bar
lightning impulse withstand voltage = 1050 kV
Short time withstand current =31.5 kA Duration of Circuit breaker=3 sec
Short circuit breaking current
Symmetrical =31.5 kA Asymmetrical =37.3 kA
It interrupts the circuit during excessive arc conditions and prevents fire. Under
normal arcing condition this will idle and does not interrupt the circuit.
SF6 circuit breakers are used in switchyard of NTPC kawas. .These breakers are
fixed , hydraulic oil operated breakers. Sulphur hexa fluoride circuit breaprotect
electrical power station and distribution systems by using interrupting electric
current , when tripped by a protective relay.
Instead of oil , air or a vacuum circuit breakers ,SF6 circuit breakers used
because it uses SF6 gas to quench the arc on opening a circuit.SF6 has excellent
dielectric, arc quenching, chemical and other physical properties.SF6 is a spark
reduces agent.
It is used for voltage range of upto 800 kV .
Specification Of SF6 Breakers:-
SF6 Breaker Name Plate - GEC ALSTHOM( France Made)
Voltage=245 kV Type= Fx22 F =50 Hz
Normal Current =2500 A Total mass of SF6 gas=29.5 kg
Total Mass of Circuit Breakers = 6030 kg
SF6 gas Pressure at 20
o
C ,1013 hPa = 7.65 bar
lightning impulse withstand voltage = 1050 kV
Short time withstand current =31.5 kA Duration of Circuit breaker=3 sec
Short circuit breaking current
Symmetrical =31.5 kA Asymmetrical =37.3 kA
Breaker Testing
For breaker Testing we have to provide current and whatever voltage available
in bus so dividing voltage/current we get resistance. Nominal resistance should
be same as calculated resistance . So for testing we getting two parameters :-
1. Resistance
2. Timing
ISOLATORS
It is a off load Device .
Isolator is a manually operated mechanical switch that isolates the faulty section
or the section of a conductor or a part of a circuit of substation meant for repair
from a healthy section in order to avoid occurrence of more severe faults.
Hence, it is also called as a disconnector or disconnecting switch. There are
different types of isolators used for different applications such as single-break
isolator, double-break isolator, bus isolator, line isolator, etc
INSULATORS
The metal which does not allow free movement of electrons or electric charge is
called as an insulator. Hence, insulators resist electricity with their high
resisting property. There are different types of insulators such as suspension
type, strain type, stray type, shackle, pin type and so on. Insulators are used for
insulation purpose while erecting electric poles with conductors to avoid short
circuit and for other insulation requirements.
There are several types of insulators but the most commonly used are pin type,
suspension type, strain insulator and shackle insulator.
For breaker Testing we have to provide current and whatever voltage available
in bus so dividing voltage/current we get resistance. Nominal resistance should
be same as calculated resistance . So for testing we getting two parameters :-
1. Resistance
2. Timing
ISOLATORS
It is a off load Device .
Isolator is a manually operated mechanical switch that isolates the faulty section
or the section of a conductor or a part of a circuit of substation meant for repair
from a healthy section in order to avoid occurrence of more severe faults.
Hence, it is also called as a disconnector or disconnecting switch. There are
different types of isolators used for different applications such as single-break
isolator, double-break isolator, bus isolator, line isolator, etc
INSULATORS
The metal which does not allow free movement of electrons or electric charge is
called as an insulator. Hence, insulators resist electricity with their high
resisting property. There are different types of insulators such as suspension
type, strain type, stray type, shackle, pin type and so on. Insulators are used for
insulation purpose while erecting electric poles with conductors to avoid short
circuit and for other insulation requirements.
There are several types of insulators but the most commonly used are pin type,
suspension type, strain insulator and shackle insulator.
1 Pin type Insulators
Pin Type Insulator
As the name suggests, the pin type insulator is secured to the cross-arm on the
pole. There is a groove on the upper end of the insulator for housing the
conductor. The conductor passes through this groove and is bound by the
annealed wire of the same material as the conductor.
Pin type insulators are used for transmission and distribution of electric power
at voltages upto 33 kV. Beyond operating voltage of 33 kV, the pin type
insulators become too bulky and hence uneconomical.
Pin Type Image
Pin Type Insulator
As the name suggests, the pin type insulator is secured to the cross-arm on the
pole. There is a groove on the upper end of the insulator for housing the
conductor. The conductor passes through this groove and is bound by the
annealed wire of the same material as the conductor.
Pin type insulators are used for transmission and distribution of electric power
at voltages upto 33 kV. Beyond operating voltage of 33 kV, the pin type
insulators become too bulky and hence uneconomical.
Pin Type Image
2 Suspension Type
Suspension Type
For high voltages (>33 kV), it is a usual practice to use suspension type
insulators shown in Figure. consist of a number of porcelain discs connected in
series by metal links in the form of a string. The conductor is suspended at the
bottom end of this string while the other end of the string is secured to the cross-
arm of the tower. Each unit or disc is designed for low voltage, say 11 kV. The
number of discs in series would obviously depend upon the working voltage.
For instance, if the working voltage is 66 kV, then six discs in series will be
provided on the string.
Tilted insulators are also used for Arc Horns Protection. Having Ring of
insulators at the end if sudden fault occurs than electrons jump to zero
potential difference end with the help of ring types structures.
Suspension Type
For high voltages (>33 kV), it is a usual practice to use suspension type
insulators shown in Figure. consist of a number of porcelain discs connected in
series by metal links in the form of a string. The conductor is suspended at the
bottom end of this string while the other end of the string is secured to the cross-
arm of the tower. Each unit or disc is designed for low voltage, say 11 kV. The
number of discs in series would obviously depend upon the working voltage.
For instance, if the working voltage is 66 kV, then six discs in series will be
provided on the string.
Tilted insulators are also used for Arc Horns Protection. Having Ring of
insulators at the end if sudden fault occurs than electrons jump to zero
potential difference end with the help of ring types structures.
Suspension Type Image
3 Strain Insulators
Strain Type Insulator
When there is a dead end of the line or there is corner or sharp curve, the line is
subjected to greater tension. In order to relieve the line of excessive tension,
strain insulators are used. For low voltage lines (< 11 kV), shackle insulators are
used as strain insulators. However, for high voltage transmission lines, strain
insulator consists of an assembly of suspension insulators as shown in Figure.
The discs of strain insulators are used in the vertical plane. When the tension in
lines is exceedingly high, at long river spans, two or more strings are used in
parallel.
4 Shackle Insulators
Shackle Type Insulator
In early days, the shackle insulators were used as strain insulators. But now a
days, they are frequently used for low voltage distribution lines. Such insulators
3 Strain Insulators
Strain Type Insulator
When there is a dead end of the line or there is corner or sharp curve, the line is
subjected to greater tension. In order to relieve the line of excessive tension,
strain insulators are used. For low voltage lines (< 11 kV), shackle insulators are
used as strain insulators. However, for high voltage transmission lines, strain
insulator consists of an assembly of suspension insulators as shown in Figure.
The discs of strain insulators are used in the vertical plane. When the tension in
lines is exceedingly high, at long river spans, two or more strings are used in
parallel.
4 Shackle Insulators
Shackle Type Insulator
In early days, the shackle insulators were used as strain insulators. But now a
days, they are frequently used for low voltage distribution lines. Such insulators
can be used either in a horizontal position or in a vertical position. They can be
directly fixed to the pole with a bolt or to the cross arm.
CAPACITATIVE VOLTAGE TRANSFORMER
A capacitor voltage transformer (CVT) is a transformer used in power systems
to step-down extra high voltage signals and provide low voltage signals either
for measurement or to operate a protective relay. It is located in the last in the
switchyard as it increases the ground resistance. Finally the voltage from CVT
in the switchyard is sent out from the station through transmission lines.
It is working same as PT but it is used for very high voltage range . it’s also
economical than PT.
EARTHING ROD
Normally un-galvanized mild steel flats are used for earthling. Separate earthing
electrodes are provided to earth the lightening arrestor whereas the other
equipments are earthed by connecting their earth leads to the rid/ser of the
ground mar
(h) Instrument Transformers:
Instrument transformers
The current and voltage transformers are together called as the
Instrument transforms
.
CURRENT TRANSFORMER
It is essentially a step up transformer which step down the current to a known
ratio. It is a type of instrument transformer designed to provide a current in its
secondary winding proportional to the alternating current flowing in its primary.
directly fixed to the pole with a bolt or to the cross arm.
CAPACITATIVE VOLTAGE TRANSFORMER
A capacitor voltage transformer (CVT) is a transformer used in power systems
to step-down extra high voltage signals and provide low voltage signals either
for measurement or to operate a protective relay. It is located in the last in the
switchyard as it increases the ground resistance. Finally the voltage from CVT
in the switchyard is sent out from the station through transmission lines.
It is working same as PT but it is used for very high voltage range . it’s also
economical than PT.
EARTHING ROD
Normally un-galvanized mild steel flats are used for earthling. Separate earthing
electrodes are provided to earth the lightening arrestor whereas the other
equipments are earthed by connecting their earth leads to the rid/ser of the
ground mar
(h) Instrument Transformers:
Instrument transformers
The current and voltage transformers are together called as the
Instrument transforms
.
CURRENT TRANSFORMER
It is essentially a step up transformer which step down the current to a known
ratio. It is a type of instrument transformer designed to provide a current in its
secondary winding proportional to the alternating current flowing in its primary.
POTENTIAL TRANSFORMER
It is essentially a step down transformer and it step downs the voltage to a
known ratio.
CAPACITOR BANKS
A Capacitor bank is a set of many identical capacitors connected in series or
parallel within a enclosure and is used for the power factor correction and basic
protection of substation These capacitor banks are acts as a source of reactive
power, and thus, the phase difference between voltage and current can be
reduced by the capacitor banks. They will increase the ripple current capacity of
the supply. It avoids undesirable characteristics in the power system. It is the
most economical method for maintaining power factor and of correction of the
power lag problems.
It is essentially a step down transformer and it step downs the voltage to a
known ratio.
CAPACITOR BANKS
A Capacitor bank is a set of many identical capacitors connected in series or
parallel within a enclosure and is used for the power factor correction and basic
protection of substation These capacitor banks are acts as a source of reactive
power, and thus, the phase difference between voltage and current can be
reduced by the capacitor banks. They will increase the ripple current capacity of
the supply. It avoids undesirable characteristics in the power system. It is the
most economical method for maintaining power factor and of correction of the
power lag problems.
RELAYS
Relay is a sensing device that makes your circuit ON or OFF. They detect the
abnormal conditions in the electrical circuits by continuously measuring the
electrical quantities, which are different under normal and faulty conditions, like
current, voltage frequency. Having detected the fault the relay operates to
complete the trip circuit, which results in the opening of the circuit breakers and
disconnect the faulty circuit. There are different types of relays:
i. Current relay
1. Over current relay
2. Definite time over current relay
3. inverse time over current relays
ii. Potential relay
iii. Auxiliary relay
iv. Solid state relays
v. Directional relays
vi. Mechanical relay
vii. Microcontroller relays
viii. Electromagnetic relay
ix. Numerical relay etc.
Relay is a sensing device that makes your circuit ON or OFF. They detect the
abnormal conditions in the electrical circuits by continuously measuring the
electrical quantities, which are different under normal and faulty conditions, like
current, voltage frequency. Having detected the fault the relay operates to
complete the trip circuit, which results in the opening of the circuit breakers and
disconnect the faulty circuit. There are different types of relays:
i. Current relay
1. Over current relay
2. Definite time over current relay
3. inverse time over current relays
ii. Potential relay
iii. Auxiliary relay
iv. Solid state relays
v. Directional relays
vi. Mechanical relay
vii. Microcontroller relays
viii. Electromagnetic relay
ix. Numerical relay etc.
AIR BREAK EARTHING SWITCH
The work of this equipment comes into picture when we want to shut down the
supply for maintenance purpose. This help to neutralize the system from
induced voltage from extra high voltage. This induced power is up to 2KV in
case of 400 KV lines.
ADDITIONAL
CONCRETE used in Switchyard:-
Power Transformers installed in the substations will have oil as cooling
and insulating medium. Oil leakage takes place during operation or
when changing the oil in the transformer. This oil spillage which can
catch fire is dangerous to the switchyard operation. So Stones is
provided to protect from fire when oil spillage takes place.
Improves substation working condition
To avoid entry of animals like Rats, snakes, Lizards etc..
As water beneath the substation may provide conductivity for
electricity ,so pebbles are provided to break the surface of water since
water surface has high conductivity ,so that flow of electricity is not
continuous.
In plain grounds when grass grows it will form moisture and it will
cause damage to transmission lines and it will also form current leakage
.Stones eliminate the growth of small weeds and plants or grass inside
the Substation.
To absorbed the heat radiated by radiator during cooling of oil.
To reduce the vibration in transformer which has been caused due to
magnetostriction in core.
Stones also prevents the accumulation of water and the formation of
puddles inside the substation.
To increase the tower footing resistance.
During Short circuit current Step and Touch potential increases. So to
reduce the step potential and touch potential when operators work on
switch yard, Concrete in the substation is provided
(Step potential : It is the potential developed between the two feet on the
ground of a man or animal when short circuit occurs. This results in flow of
current in the body leads to electrical shock.
Touch potential: It is the potential that is developed between the ground and
the body of the equipment when a person touches the body during fault
condition. When operating personnel touch an electrical equipment during short
The work of this equipment comes into picture when we want to shut down the
supply for maintenance purpose. This help to neutralize the system from
induced voltage from extra high voltage. This induced power is up to 2KV in
case of 400 KV lines.
ADDITIONAL
CONCRETE used in Switchyard:-
Power Transformers installed in the substations will have oil as cooling
and insulating medium. Oil leakage takes place during operation or
when changing the oil in the transformer. This oil spillage which can
catch fire is dangerous to the switchyard operation. So Stones is
provided to protect from fire when oil spillage takes place.
Improves substation working condition
To avoid entry of animals like Rats, snakes, Lizards etc..
As water beneath the substation may provide conductivity for
electricity ,so pebbles are provided to break the surface of water since
water surface has high conductivity ,so that flow of electricity is not
continuous.
In plain grounds when grass grows it will form moisture and it will
cause damage to transmission lines and it will also form current leakage
.Stones eliminate the growth of small weeds and plants or grass inside
the Substation.
To absorbed the heat radiated by radiator during cooling of oil.
To reduce the vibration in transformer which has been caused due to
magnetostriction in core.
Stones also prevents the accumulation of water and the formation of
puddles inside the substation.
To increase the tower footing resistance.
During Short circuit current Step and Touch potential increases. So to
reduce the step potential and touch potential when operators work on
switch yard, Concrete in the substation is provided
(Step potential : It is the potential developed between the two feet on the
ground of a man or animal when short circuit occurs. This results in flow of
current in the body leads to electrical shock.
Touch potential: It is the potential that is developed between the ground and
the body of the equipment when a person touches the body during fault
condition. When operating personnel touch an electrical equipment during short
circuit condition, fault current flows through the human body. This is defined as
touch potential.)
POWER LINE CARRIER COMMUNICATION (WAVE TRAP):-
These are used for both Communication as well as protection purpose. It is a
communication technology that enables sending data over existing power
cables. This means that, with just power cables running to an electronic device
(for example) one can both power it up and at the same time control/retrieve
data from it in a half-duplex manner.
Power-line communication (PLC) carries data on a conductor that is also used
simultaneously for AC electric power transmission or electric power
distribution to consumers. It is also known as power-line carrier, power-line
digital subscriber line (PDSL), mains communication, power-line
telecommunications, or power-line networking (PLN).
A wide range of power-line communication technologies are needed for
different applications, ranging from home automation to Internet access which
is often called broadband over power lines (BPL). Most PLC technologies limit
themselves to one type of wires (such as premises wiring within a single
building), but some can cross between two levels (for example, both the
distribution network and premises wiring). Various data rates and frequencies
are used in different situations.
A number of difficult technical problems are common between wireless and
power-line communication, notably those of spread spectrum radio signals
regoperating in a crowded environment. Radio interference, for example, has
long been a concern of amateur radio groups.
There is Noise or line sound in Switchyard Due to Leakage current
There is 18 Bays in Switchyard of Kawas plant
8 Line
[4 GT + 2 ST] = 6 Generator Bays
2 Station Transformer Bays
1 Transfer Bus
1 Bus Coupler
Each bays included 4 isolators, 1 circuit breakers and 3 earth switch.
touch potential.)
POWER LINE CARRIER COMMUNICATION (WAVE TRAP):-
These are used for both Communication as well as protection purpose. It is a
communication technology that enables sending data over existing power
cables. This means that, with just power cables running to an electronic device
(for example) one can both power it up and at the same time control/retrieve
data from it in a half-duplex manner.
Power-line communication (PLC) carries data on a conductor that is also used
simultaneously for AC electric power transmission or electric power
distribution to consumers. It is also known as power-line carrier, power-line
digital subscriber line (PDSL), mains communication, power-line
telecommunications, or power-line networking (PLN).
A wide range of power-line communication technologies are needed for
different applications, ranging from home automation to Internet access which
is often called broadband over power lines (BPL). Most PLC technologies limit
themselves to one type of wires (such as premises wiring within a single
building), but some can cross between two levels (for example, both the
distribution network and premises wiring). Various data rates and frequencies
are used in different situations.
A number of difficult technical problems are common between wireless and
power-line communication, notably those of spread spectrum radio signals
regoperating in a crowded environment. Radio interference, for example, has
long been a concern of amateur radio groups.
There is Noise or line sound in Switchyard Due to Leakage current
There is 18 Bays in Switchyard of Kawas plant
8 Line
[4 GT + 2 ST] = 6 Generator Bays
2 Station Transformer Bays
1 Transfer Bus
1 Bus Coupler
Each bays included 4 isolators, 1 circuit breakers and 3 earth switch.
Figure Switchyard of NTPC kawas
SWITCHGEAR :-
The term switchgear, used in association with the electric power system, or grid,
refers to the combination of electrical disconnects, fuses and/or circuit breakers
used to isolate electrical equipment. Switchgear is used both to de-energize
equipment to allow work to be done and to clear faults downstream. The very
earliest central power stations used simple open knife switches, mounted on
insulating panels of marble or asbestos. Power levels and voltages rapidly
escalated, making open manually-operated switches too dangerous to use for
anything other than isolation of a de-energized circuit. Oil-filled equipment
allowed arc energy to be contained and safely controlled. By the early 20th
century, a switchgear line-up would be a metal-enclosed structure with
electrically-operated switching elements, using oil circuit breakers. Today, oil-
filled equipment has largely been replaced by air-blast, vacuum, or SF6
equipment, allowing large currents and power levels to be safely controlled by
automatic equipment incorporating digital controls, protection, metering and
communications
A piece of switchgear may be a simple open air isolator switch or it may be
insulated by some other substance. An effective although more costly form of
switchgear is "gas insulated switchgear" (GIS), where the conductors and
contacts are insulated by pressurized (SF6) sulfur hexafluoride gas. Other
common types are oil [or vacuum] insulated switchgear. Circuit breakers are a
special type of switchgear that are able to interrupt fault currents.
INTRODUCTION
Switchgear is one that makes or breaks the electrical circuit. It is a switching
device that opens& closes a circuit that defined as apparatus used for switching,
Lon rolling & protecting the electrical circuit & equipment’s. The switchgear
equipment is essentially concerned with switching & interrupting currents
either under normal or abnormal operating conditions. The tubular switch with
ordinary fuse is simplest form of switchgear & is used to control & protect&
other equipment’s in homes, offices etc. For circuits of higher ratings, a High
Rupturing Capacity (H.R.C) fuse in condition with a switch may serve the
purpose of controlling &protecting the circuit. However such switchgear cannot
The term switchgear, used in association with the electric power system, or grid,
refers to the combination of electrical disconnects, fuses and/or circuit breakers
used to isolate electrical equipment. Switchgear is used both to de-energize
equipment to allow work to be done and to clear faults downstream. The very
earliest central power stations used simple open knife switches, mounted on
insulating panels of marble or asbestos. Power levels and voltages rapidly
escalated, making open manually-operated switches too dangerous to use for
anything other than isolation of a de-energized circuit. Oil-filled equipment
allowed arc energy to be contained and safely controlled. By the early 20th
century, a switchgear line-up would be a metal-enclosed structure with
electrically-operated switching elements, using oil circuit breakers. Today, oil-
filled equipment has largely been replaced by air-blast, vacuum, or SF6
equipment, allowing large currents and power levels to be safely controlled by
automatic equipment incorporating digital controls, protection, metering and
communications
A piece of switchgear may be a simple open air isolator switch or it may be
insulated by some other substance. An effective although more costly form of
switchgear is "gas insulated switchgear" (GIS), where the conductors and
contacts are insulated by pressurized (SF6) sulfur hexafluoride gas. Other
common types are oil [or vacuum] insulated switchgear. Circuit breakers are a
special type of switchgear that are able to interrupt fault currents.
INTRODUCTION
Switchgear is one that makes or breaks the electrical circuit. It is a switching
device that opens& closes a circuit that defined as apparatus used for switching,
Lon rolling & protecting the electrical circuit & equipment’s. The switchgear
equipment is essentially concerned with switching & interrupting currents
either under normal or abnormal operating conditions. The tubular switch with
ordinary fuse is simplest form of switchgear & is used to control & protect&
other equipment’s in homes, offices etc. For circuits of higher ratings, a High
Rupturing Capacity (H.R.C) fuse in condition with a switch may serve the
purpose of controlling &protecting the circuit. However such switchgear cannot
be used profitably on high voltage system (3.3 KV) for 2 reasons. Firstly, when
a fuse blows, it takes some time to replace it &consequently there is
interruption of service to customer. Secondly, the fuse cannot successfully
interrupt large currents that result from the High Voltage System. In order to
interrupt heavy fault currents, automatic circuit breakers are used. There are
very few types of circuit breakers they are VCB, OCB, and SF6 gas circuit
breaker. The most expensive circuit breaker is the SF6 type due to gas. There
are various companies which manufacture these circuit breakers: VOLTAS,
JYOTI, and KIRLOSKAR. Switchgear includes switches, fuses, circuit
breakers, relays & other equipment’s.
TYPES OF SWITCHGEAR: -
1. ISOLATOR
An isolator is one that can break the electrical circuit when the circuit is to
be switched on at no load. These are used in various circuits for isolating the
certain portion when required for maintenance etc. An operating mechanism
box normally installed at ground level drives the isolator. The box has an
operating mechanism in addition to its contactor circuit and auxiliary
contacts may be solenoid operated pneumatic three phase motor or DC
motor transmitting through a spur gear to the torsion shaft of the isolator.
Certain interlocks are also provided with the isolator these are
1. Isolator cannot operate unless breaker is open
2. Bus 1 and bus 2 isolators cannot be closed simultaneously
3. The interlock can be bypass in the event of closing of bus coupler
breaker.
4. No isolator can operate when the corresponding earth switch is on
a fuse blows, it takes some time to replace it &consequently there is
interruption of service to customer. Secondly, the fuse cannot successfully
interrupt large currents that result from the High Voltage System. In order to
interrupt heavy fault currents, automatic circuit breakers are used. There are
very few types of circuit breakers they are VCB, OCB, and SF6 gas circuit
breaker. The most expensive circuit breaker is the SF6 type due to gas. There
are various companies which manufacture these circuit breakers: VOLTAS,
JYOTI, and KIRLOSKAR. Switchgear includes switches, fuses, circuit
breakers, relays & other equipment’s.
TYPES OF SWITCHGEAR: -
1. ISOLATOR
An isolator is one that can break the electrical circuit when the circuit is to
be switched on at no load. These are used in various circuits for isolating the
certain portion when required for maintenance etc. An operating mechanism
box normally installed at ground level drives the isolator. The box has an
operating mechanism in addition to its contactor circuit and auxiliary
contacts may be solenoid operated pneumatic three phase motor or DC
motor transmitting through a spur gear to the torsion shaft of the isolator.
Certain interlocks are also provided with the isolator these are
1. Isolator cannot operate unless breaker is open
2. Bus 1 and bus 2 isolators cannot be closed simultaneously
3. The interlock can be bypass in the event of closing of bus coupler
breaker.
4. No isolator can operate when the corresponding earth switch is on
2. SWITCHING ISOLATOR
Switching isolator is capable of:
1. Interrupting charging current
2. Interrupting transformer magnetizing current
3. Load transformer switching. Its main application is in connection
with the transformer feeder as the unit makes it possible to switch gear
one transformer while the other is still on load.
3. CIRCUIT BREAKER
One which can make or break the circuit on load and even on faults is
referred to as circuit breakers. This equipment is the most important and
is heavy duty equipment mainly utilized for protection of various
circuits and operations on load. Normally circuit breakers installed are
accompanied by isolators.
4. LOAD BREAK SWITCHES
These are those interrupting devices which can make or break circuits. These
are normally on same circuit, which are backed by circuit breakers
5. EARTH SWITCHES
Devices which are used normally to earth a particular system, to avoid any
accident happening due to induction on account of live adjoining circuits.
These equipment’s do not handle any appreciable current at all. Apart from
this equipment there are a number of relays etc. which are used in
switchgear.
LT SWITCHGEAR
In LT switchgear there is no interlocking. It is classified in following ways:-
Switching isolator is capable of:
1. Interrupting charging current
2. Interrupting transformer magnetizing current
3. Load transformer switching. Its main application is in connection
with the transformer feeder as the unit makes it possible to switch gear
one transformer while the other is still on load.
3. CIRCUIT BREAKER
One which can make or break the circuit on load and even on faults is
referred to as circuit breakers. This equipment is the most important and
is heavy duty equipment mainly utilized for protection of various
circuits and operations on load. Normally circuit breakers installed are
accompanied by isolators.
4. LOAD BREAK SWITCHES
These are those interrupting devices which can make or break circuits. These
are normally on same circuit, which are backed by circuit breakers
5. EARTH SWITCHES
Devices which are used normally to earth a particular system, to avoid any
accident happening due to induction on account of live adjoining circuits.
These equipment’s do not handle any appreciable current at all. Apart from
this equipment there are a number of relays etc. which are used in
switchgear.
LT SWITCHGEAR
In LT switchgear there is no interlocking. It is classified in following ways:-
1. MAIN SWITCH
Main switch is control equipment which controls or disconnects the main
supply. The main switch for 3 phase supply is available for the range 32A,
63A, 100A, 200A, 300A at 500V grade.
2. FUSES
With Avery high generating capacity of the modern power stations
extremely heavy currents would flow in the fault and the fuse clearing the
fault would be required to withstand extremely heavy stress in process. It is
used for supplying power to auxiliaries with backup fuse protection. With
fuses, quick break, quick make and double break switch fuses for 63A and
100A, switch fuses for 200A, 400A, 600A, 800A and 1000A are used.
3. CONTACTORS
AC Contractors are 3 poles suitable for D.O.L Starting of motors and
protecting the connected motors.
Main switch is control equipment which controls or disconnects the main
supply. The main switch for 3 phase supply is available for the range 32A,
63A, 100A, 200A, 300A at 500V grade.
2. FUSES
With Avery high generating capacity of the modern power stations
extremely heavy currents would flow in the fault and the fuse clearing the
fault would be required to withstand extremely heavy stress in process. It is
used for supplying power to auxiliaries with backup fuse protection. With
fuses, quick break, quick make and double break switch fuses for 63A and
100A, switch fuses for 200A, 400A, 600A, 800A and 1000A are used.
3. CONTACTORS
AC Contractors are 3 poles suitable for D.O.L Starting of motors and
protecting the connected motors.
4. OVERLOAD RELAY
For overload protection, thermal overload relay are best suited for this purpose.
They operate due to the action of heat generated by passage of current through
relay element.
5. AIR CIRCUIT BREAKERS
It is seen that use of oil in circuit breaker may cause a fire. So in all circuits
breakers at large capacity air at high pressure is used which is maximum at the
time of quick tripping of contacts. This reduces the possibility of sparking. The
pressure may vary from 50-60kg/cm^2 for high and medium capacity circuit
breakers.
HT SWITCHGEAR
1. MINIMUM OIL CIRCUIT BREAKER
These use oil as quenching medium. It comprises of simple dead tank row
pursuing projection from it. The moving contracts are carried on an iron arm
lifted by a long insulating tension rod and are closed simultaneously pneumatic
For overload protection, thermal overload relay are best suited for this purpose.
They operate due to the action of heat generated by passage of current through
relay element.
5. AIR CIRCUIT BREAKERS
It is seen that use of oil in circuit breaker may cause a fire. So in all circuits
breakers at large capacity air at high pressure is used which is maximum at the
time of quick tripping of contacts. This reduces the possibility of sparking. The
pressure may vary from 50-60kg/cm^2 for high and medium capacity circuit
breakers.
HT SWITCHGEAR
1. MINIMUM OIL CIRCUIT BREAKER
These use oil as quenching medium. It comprises of simple dead tank row
pursuing projection from it. The moving contracts are carried on an iron arm
lifted by a long insulating tension rod and are closed simultaneously pneumatic
operating mechanism by means of tensions but throw off spring to be provided
at mouth of the control the main current within the controlled device.
2. AIR CIRCUIT BREAKER
at mouth of the control the main current within the controlled device.
2. AIR CIRCUIT BREAKER
In this the compressed air pressure around 15 kg per cm^2 is used for
extinction of arc caused by flow of air around the moving circuit. The breaker is
closed by applying pressure at lower opening and opened by applying pressure
at upper opening. When contacts operate, the cold air rushes around the
movable contacts and blown the arc:
It has the following advantages over OCB:-
i. Fire hazard due to oil are eliminated.
ii. Operation takes place quickly.
iii. There is less burning of contacts since the duration is short and
consistent.
iv. Facility for frequent operation since the cooling medium is
replaced constantly.
SF6 Breakers used in Switchgear which is Movable and spring operator.
SF6 SPECIFICATION
Pressure=5.5 bar F=50 Hz Current = 630 A
SF6 filling at pressure at 20
o
C Voltage=1.2 kV
System breaking Capacity =40 kA
System making Capacity = 100 kA
System making capacity is more then System Breaking Capacity
BATTERY USED IN SWITCHGEAR
Lead Acid:-
700 Ah 125 volts (1 cell = 2 V) 67 cells
10 % charging an discharging capacity.
Ni-Cd :-
1500 Ah 16 cells
20 % charging and discharging capacity.
extinction of arc caused by flow of air around the moving circuit. The breaker is
closed by applying pressure at lower opening and opened by applying pressure
at upper opening. When contacts operate, the cold air rushes around the
movable contacts and blown the arc:
It has the following advantages over OCB:-
i. Fire hazard due to oil are eliminated.
ii. Operation takes place quickly.
iii. There is less burning of contacts since the duration is short and
consistent.
iv. Facility for frequent operation since the cooling medium is
replaced constantly.
SF6 Breakers used in Switchgear which is Movable and spring operator.
SF6 SPECIFICATION
Pressure=5.5 bar F=50 Hz Current = 630 A
SF6 filling at pressure at 20
o
C Voltage=1.2 kV
System breaking Capacity =40 kA
System making Capacity = 100 kA
System making capacity is more then System Breaking Capacity
BATTERY USED IN SWITCHGEAR
Lead Acid:-
700 Ah 125 volts (1 cell = 2 V) 67 cells
10 % charging an discharging capacity.
Ni-Cd :-
1500 Ah 16 cells
20 % charging and discharging capacity.
IEEE DEVICE NUMBERS AND FUNCTIONS
FOR SWITCHGEAR APPARATUS
The devices in switching equipments are referred to by numbers, with
appropriate suffix letters when necessary, according to the functions they
perform.
These numbers are based on a system adopted as standard for automatic
switchgear by IEEE, and incorporated in American Standard C37.2-1979. This
system is used in connection diagrams, in instruction books, and in
specifications.
Device number Definition and function
1 Master element is the initiating device, such as a control switch, voltage
relay, float switch etc., that serves either directly, or through such permissive
devices as protective and time-delay relays, to place an equipment in or out of
operation.
2 Time-delay starting or closing relay is a device that functions to give a
desired amount of time delay before or after any point of operation in a
switching sequence or protective relay system, except as specifically provided
by device functions 48, 62 and 79 described later.
3 Checking or interlocking relay is a device that operates in response to the
position of a number of other devices, (or to a number of predetermined
conditions), in an equipment to allow an operating sequence to proceed, to stop,
or to provide a check of the position of these devices or of these conditions for
any purpose.
4 Master contactor is a device, generally controlled by device No. 1 or
equivalent, and the required permissive and protective devices that serve to
make and break the necessary control circuits to place an equipment into
operation under the desired conditions and to take it out of operation under
other or abnormal conditions.
5 Stopping device is a control device used primarily to shut down an equipment
and hold it out of operation. [This device may be manually or electrically
actuated, but excludes the function of electrical lockout (see device function 86)
on abnormal conditions.]
FOR SWITCHGEAR APPARATUS
The devices in switching equipments are referred to by numbers, with
appropriate suffix letters when necessary, according to the functions they
perform.
These numbers are based on a system adopted as standard for automatic
switchgear by IEEE, and incorporated in American Standard C37.2-1979. This
system is used in connection diagrams, in instruction books, and in
specifications.
Device number Definition and function
1 Master element is the initiating device, such as a control switch, voltage
relay, float switch etc., that serves either directly, or through such permissive
devices as protective and time-delay relays, to place an equipment in or out of
operation.
2 Time-delay starting or closing relay is a device that functions to give a
desired amount of time delay before or after any point of operation in a
switching sequence or protective relay system, except as specifically provided
by device functions 48, 62 and 79 described later.
3 Checking or interlocking relay is a device that operates in response to the
position of a number of other devices, (or to a number of predetermined
conditions), in an equipment to allow an operating sequence to proceed, to stop,
or to provide a check of the position of these devices or of these conditions for
any purpose.
4 Master contactor is a device, generally controlled by device No. 1 or
equivalent, and the required permissive and protective devices that serve to
make and break the necessary control circuits to place an equipment into
operation under the desired conditions and to take it out of operation under
other or abnormal conditions.
5 Stopping device is a control device used primarily to shut down an equipment
and hold it out of operation. [This device may be manually or electrically
actuated, but excludes the function of electrical lockout (see device function 86)
on abnormal conditions.]
6 Starting circuit breaker is a device whose principal function is to connect a
machine to its source of starting voltage.
7 Rate-of-rise relay is a relay that functions on an excessive rate of rise of
current.
8 Control power disconnecting device is a disconnecting device, such as a
knife switch, circuit breaker, or pull-out fuse block, used for the purpose of
respectively connecting and disconnecting the source of control power to and
from the control bus or equipment.
9 Reversing device is used for the purpose of reversing a machine field or for
performing any other reversing functions.
10 Unit sequence switch is used to change the sequence in which units may be
placed in and out of service in multiple-unit equipment.
11 Multifunction device is a device that performs three or more comparatively
important functions that could only be designated by combining several of these
device function numbers. All of the functions performed by device 11 shall be
defined in the drawing legend or device function list.
12 Over speed device is usually a direct connected speed switch that functions
on machine over speed.
13 Synchronous-speed device, such as a centrifugal speed switch, a slip
frequency relay, a voltage relay, an undercurrent relay, or any other type of
device that operates at approximately
the synchronous speed of a machine.
14 Under speed device functions when the speed of a machine falls below a
pre-determined value.
machine to its source of starting voltage.
7 Rate-of-rise relay is a relay that functions on an excessive rate of rise of
current.
8 Control power disconnecting device is a disconnecting device, such as a
knife switch, circuit breaker, or pull-out fuse block, used for the purpose of
respectively connecting and disconnecting the source of control power to and
from the control bus or equipment.
9 Reversing device is used for the purpose of reversing a machine field or for
performing any other reversing functions.
10 Unit sequence switch is used to change the sequence in which units may be
placed in and out of service in multiple-unit equipment.
11 Multifunction device is a device that performs three or more comparatively
important functions that could only be designated by combining several of these
device function numbers. All of the functions performed by device 11 shall be
defined in the drawing legend or device function list.
12 Over speed device is usually a direct connected speed switch that functions
on machine over speed.
13 Synchronous-speed device, such as a centrifugal speed switch, a slip
frequency relay, a voltage relay, an undercurrent relay, or any other type of
device that operates at approximately
the synchronous speed of a machine.
14 Under speed device functions when the speed of a machine falls below a
pre-determined value.
15 Speed or frequency matching device functions to match and hold the speed
or the frequency of a machine or of a system equal to, or approximately equal
to, that of another machine, source, or system.
16 Reserved for future application
17 Shunting or discharge switch serves to open or to close a shunting circuit
around any piece of apparatus (except a resistor), such as a machine field, a
machine armature, a capacitor, or a reactor.
18 Accelerating or decelerating device is used to close or to cause the closing
of circuits that are used to increase or decrease the speed of a machine.
19 Starting-to-running transition contactor is a device that operates to
initiate or cause the automatic transfer of a machine from the starting to the
running power connection.
20 Electrically operated valve is an electrically operated, controlled, or
monitored valve used in a fluid, air, gas, or vacuum line.
21 Distance relay is a relay that functions when the circuit admittance,
impedance, or reactance increases or decreases beyond a predetermined value.
22 Equalizer circuit breaker is a breaker that serves to control or to make and
break the equalizer or the current balancing connections for a machine field, or
for regulating equipment, in a multiple unit installation.
23 Temperature control device functions to raise or to lower the temperature
of a machine or other apparatus, or of any medium, when its temperature falls
below or rises above a predetermined value.
24 Volts per hertz relay is a relay that functions when the ratio of voltage to
frequency exceeds a preset value. The relay may have an instantaneous or a
time characteristic.
or the frequency of a machine or of a system equal to, or approximately equal
to, that of another machine, source, or system.
16 Reserved for future application
17 Shunting or discharge switch serves to open or to close a shunting circuit
around any piece of apparatus (except a resistor), such as a machine field, a
machine armature, a capacitor, or a reactor.
18 Accelerating or decelerating device is used to close or to cause the closing
of circuits that are used to increase or decrease the speed of a machine.
19 Starting-to-running transition contactor is a device that operates to
initiate or cause the automatic transfer of a machine from the starting to the
running power connection.
20 Electrically operated valve is an electrically operated, controlled, or
monitored valve used in a fluid, air, gas, or vacuum line.
21 Distance relay is a relay that functions when the circuit admittance,
impedance, or reactance increases or decreases beyond a predetermined value.
22 Equalizer circuit breaker is a breaker that serves to control or to make and
break the equalizer or the current balancing connections for a machine field, or
for regulating equipment, in a multiple unit installation.
23 Temperature control device functions to raise or to lower the temperature
of a machine or other apparatus, or of any medium, when its temperature falls
below or rises above a predetermined value.
24 Volts per hertz relay is a relay that functions when the ratio of voltage to
frequency exceeds a preset value. The relay may have an instantaneous or a
time characteristic.
25 Synchronizing or synchronism check device operates when two ac circuits
are within the desired limits of frequency, phase angle, or voltage to permit or to
cause the paralleling of these two circuits.
26 Apparatus thermal device functions when the temperature of the protected
apparatus (other than the load carrying windings of machines and transformers
as covered by device function number 49) or of a liquid or other medium
exceeds a predetermined value; or when the temperature of the protected
apparatus or of any medium decreases below a predetermined value.
27 Under voltage relay is a relay that operates when its input voltage is less
than a predetermined value.
28 Flame detector is a device that monitors the presence of the pilot or main
flame in such apparatus as a gas turbine or a steam boiler.
29 Isolating contactor is used expressly for disconnecting one circuit from
another for the purposes of emergency operation, maintenance, or test.
30 Annunciator relay is a non-automatically reset device that gives a number
of separate visual indications upon the functioning of protective devices and
that may also be arranged to perform a lock-out function.
31 Separate excitation device connects a circuit, such as the shunt field of a
synchronous converter, to a source of separate excitation during the starting
sequence; or one which energizes the excitation and ignition circuits of a power
rectifier.
32 Directional power relay is a relay that operates on a predetermined value of
power flow in a given direction or upon reverse power flow such as that
resulting from the motoring of a generator upon loss of its prime mover.
are within the desired limits of frequency, phase angle, or voltage to permit or to
cause the paralleling of these two circuits.
26 Apparatus thermal device functions when the temperature of the protected
apparatus (other than the load carrying windings of machines and transformers
as covered by device function number 49) or of a liquid or other medium
exceeds a predetermined value; or when the temperature of the protected
apparatus or of any medium decreases below a predetermined value.
27 Under voltage relay is a relay that operates when its input voltage is less
than a predetermined value.
28 Flame detector is a device that monitors the presence of the pilot or main
flame in such apparatus as a gas turbine or a steam boiler.
29 Isolating contactor is used expressly for disconnecting one circuit from
another for the purposes of emergency operation, maintenance, or test.
30 Annunciator relay is a non-automatically reset device that gives a number
of separate visual indications upon the functioning of protective devices and
that may also be arranged to perform a lock-out function.
31 Separate excitation device connects a circuit, such as the shunt field of a
synchronous converter, to a source of separate excitation during the starting
sequence; or one which energizes the excitation and ignition circuits of a power
rectifier.
32 Directional power relay is a relay that operates on a predetermined value of
power flow in a given direction or upon reverse power flow such as that
resulting from the motoring of a generator upon loss of its prime mover.
33 Position switch makes or breaks contact when the main device or piece of
apparatus that has no device function number reaches a given position.
34 Master sequence device is a device such as a motor operated multi-contact
switch, or the equivalent, or a programming device, such as a computer, that
establishes or determines the operating sequence of the major devices in an
equipment during starting and stopping or during other sequential switching
operations.
35 Brush-operating or slip-ring short circuiting device is used for raising,
lowering or shifting the brushes of a machine; short-circuiting its slip rings; or
engaging or disengaging the contacts of a mechanical rectifier.
36 Polarity or polarizing voltage device operates, or permits the operation of,
another device on a predetermined polarity only or that verifies the presence of
a polarizing voltage in an equipment.
37 Undercurrent or under power relay functions when the current or power
flow decreases below a predetermined value.
38 Bearing protective device functions on excessive bearing temperature or on
other abnormal mechanical conditions associated with the bearing, such as
undue wear, which may eventually result in excessive bearing temperature or
failure.
39 Mechanical condition monitor is a device that functions upon the
occurrence of an abnormal mechanical condition (except that associated with
bearings as covered under device function 38), such as excessive vibration,
eccentricity, expansion, shock, tilting, or seal failure.
40 Field relay functions on a given or\ abnormally low value or failure of
machine field current, or on an excessive value of the reactive component of
armature current in an ac machine indicating abnormally low field excitation.
apparatus that has no device function number reaches a given position.
34 Master sequence device is a device such as a motor operated multi-contact
switch, or the equivalent, or a programming device, such as a computer, that
establishes or determines the operating sequence of the major devices in an
equipment during starting and stopping or during other sequential switching
operations.
35 Brush-operating or slip-ring short circuiting device is used for raising,
lowering or shifting the brushes of a machine; short-circuiting its slip rings; or
engaging or disengaging the contacts of a mechanical rectifier.
36 Polarity or polarizing voltage device operates, or permits the operation of,
another device on a predetermined polarity only or that verifies the presence of
a polarizing voltage in an equipment.
37 Undercurrent or under power relay functions when the current or power
flow decreases below a predetermined value.
38 Bearing protective device functions on excessive bearing temperature or on
other abnormal mechanical conditions associated with the bearing, such as
undue wear, which may eventually result in excessive bearing temperature or
failure.
39 Mechanical condition monitor is a device that functions upon the
occurrence of an abnormal mechanical condition (except that associated with
bearings as covered under device function 38), such as excessive vibration,
eccentricity, expansion, shock, tilting, or seal failure.
40 Field relay functions on a given or\ abnormally low value or failure of
machine field current, or on an excessive value of the reactive component of
armature current in an ac machine indicating abnormally low field excitation.
41 Field circuit breaker is a device that functions to apply or remove the field
excitation of a machine.
42 Running circuit breaker is a device whose principal function is to connect
a machine to its source of running or operating voltage. This function may also
be used for a device, such as a contactor, that is used in series with a circuit
breaker or other fault protecting means, primarily for frequent opening and
closing of the circuit.
43 Manual transfer or selector device is a manually operated device that
transfers the control circuits in order to modify the plan of operation of the
switching equipment or of some of the devices.
44 Unit sequence starting relay is a relay that functions to start the next
available unit in multiple unit equipment upon the failure or non-availability of
the normally preceding unit.
45 Atmospheric condition monitor is a device that functions upon the
occurrence of an abnormal atmospheric condition, such as damaging fumes,
explosive mixtures, smoke, or fire.
46 Reverse-phase or phase-balance current relay is a relay that functions
when the poly-phase currents are of reverse phase sequence or when the poly-
phase currents are unbalanced or contain negative phase-sequence components
above a given amount.
47 Phase-sequence or phase-balance voltage relay functions upon a
predetermined value of poly-phase voltage in the desired phase sequence, or
when the poly-phase voltages are unbalanced, or when the negative phase-
sequence voltage exceeds a given amount.
48 Incomplete sequence relay is a relay that generally returns the equipment to
the normal, or off, position and locks it out if the normal starting, operating, or
stopping sequence is not properly completed within a predetermined time. If the
device is used for alarm purposes only, it should preferably be designated as
48A (alarm).
excitation of a machine.
42 Running circuit breaker is a device whose principal function is to connect
a machine to its source of running or operating voltage. This function may also
be used for a device, such as a contactor, that is used in series with a circuit
breaker or other fault protecting means, primarily for frequent opening and
closing of the circuit.
43 Manual transfer or selector device is a manually operated device that
transfers the control circuits in order to modify the plan of operation of the
switching equipment or of some of the devices.
44 Unit sequence starting relay is a relay that functions to start the next
available unit in multiple unit equipment upon the failure or non-availability of
the normally preceding unit.
45 Atmospheric condition monitor is a device that functions upon the
occurrence of an abnormal atmospheric condition, such as damaging fumes,
explosive mixtures, smoke, or fire.
46 Reverse-phase or phase-balance current relay is a relay that functions
when the poly-phase currents are of reverse phase sequence or when the poly-
phase currents are unbalanced or contain negative phase-sequence components
above a given amount.
47 Phase-sequence or phase-balance voltage relay functions upon a
predetermined value of poly-phase voltage in the desired phase sequence, or
when the poly-phase voltages are unbalanced, or when the negative phase-
sequence voltage exceeds a given amount.
48 Incomplete sequence relay is a relay that generally returns the equipment to
the normal, or off, position and locks it out if the normal starting, operating, or
stopping sequence is not properly completed within a predetermined time. If the
device is used for alarm purposes only, it should preferably be designated as
48A (alarm).
49 Machine or transformer thermal relay is a relay that functions when the
temperature of a machine armature winding or other load-carrying winding or
element of a machine or power transformer exceeds a predetermined value.
50 Instantaneous overcurrent relay is a relay that functions instantaneously
on an excessive value of current.
51 Ac time overcurrent relay is a relay with either a definite or inverse time
characteristic that functions when the ac input current exceeds a predetermined
value, and in which the input current and operating time are independently
related or inversely related through a substantial portion of the performance
range.
52 Ac circuit breaker is a device that is used to close and interrupt an ac power
circuit under normal conditions or to interrupt this circuit under fault or
emergency conditions.
53 Exciter or dc generator relay is a relay that forces the dc machine field
excitation to build up during starting or that functions when the machine voltage
has built up to a given value.
54 Turning gear engaging device is an electrically operated, controlled, or
monitored device that functions to cause the turning gear to engage (or
disengage) the machine shaft.
55 Power factor relay is a relay that operates when the power factor in an ac
circuit rises above or falls below a predetermined value.
56 Field application relay is a relay that automatically controls the application
of the field excitation to an ac motor at some predetermined point in the slip
cycle.
temperature of a machine armature winding or other load-carrying winding or
element of a machine or power transformer exceeds a predetermined value.
50 Instantaneous overcurrent relay is a relay that functions instantaneously
on an excessive value of current.
51 Ac time overcurrent relay is a relay with either a definite or inverse time
characteristic that functions when the ac input current exceeds a predetermined
value, and in which the input current and operating time are independently
related or inversely related through a substantial portion of the performance
range.
52 Ac circuit breaker is a device that is used to close and interrupt an ac power
circuit under normal conditions or to interrupt this circuit under fault or
emergency conditions.
53 Exciter or dc generator relay is a relay that forces the dc machine field
excitation to build up during starting or that functions when the machine voltage
has built up to a given value.
54 Turning gear engaging device is an electrically operated, controlled, or
monitored device that functions to cause the turning gear to engage (or
disengage) the machine shaft.
55 Power factor relay is a relay that operates when the power factor in an ac
circuit rises above or falls below a predetermined value.
56 Field application relay is a relay that automatically controls the application
of the field excitation to an ac motor at some predetermined point in the slip
cycle.
57 Short-circuiting or grounding device is a primary circuit switching device
that functions to short circuit or ground a circuit in response to automatic or
manual means.
58 Rectification failure relay is a device that functions if a power rectifier fails
to conduct or block properly.
59 Overvoltage relay is a relay that operates when its input voltage is higher
than a predetermined value.
60 Voltage or current balance relay is a relay that operates on a given
difference in voltage, or current input or output, of two circuits.
61 Density switch or sensor is a device that operates on a given value, or a
given rate of change, of gas density.
62 Time-delay stopping or opening relay is a time-delay relay that serves in
conjunction with the device that initiates the shutdown, stopping, or opening
operation in an automatic sequence or protective relay system.
63 Pressure switch is a switch that operates on given values, or on a given rate
of change, of pressure.
64 Ground detector relay is a relay that operates upon failure of machine or
other apparatus insulation to ground, or on flashover of a dc machine to ground.
65 Governor is the assembly of fluid, electrical, or mechanical control
equipment used for regulating the flow of water, steam, or other media to the
prime mover for such purposes as starting, holding speed or load, or stopping.
66 Notching or jogging device functions to allow only a specified number of
operations of a given device or equipment, or a specified number of successive
operations within a given time of each other. It is also a device that functions to
energize a circuit periodically or for fractions of specified time intervals, or that
is used to permit intermittent acceleration or jogging of a machine at low speeds
for mechanical positioning.
that functions to short circuit or ground a circuit in response to automatic or
manual means.
58 Rectification failure relay is a device that functions if a power rectifier fails
to conduct or block properly.
59 Overvoltage relay is a relay that operates when its input voltage is higher
than a predetermined value.
60 Voltage or current balance relay is a relay that operates on a given
difference in voltage, or current input or output, of two circuits.
61 Density switch or sensor is a device that operates on a given value, or a
given rate of change, of gas density.
62 Time-delay stopping or opening relay is a time-delay relay that serves in
conjunction with the device that initiates the shutdown, stopping, or opening
operation in an automatic sequence or protective relay system.
63 Pressure switch is a switch that operates on given values, or on a given rate
of change, of pressure.
64 Ground detector relay is a relay that operates upon failure of machine or
other apparatus insulation to ground, or on flashover of a dc machine to ground.
65 Governor is the assembly of fluid, electrical, or mechanical control
equipment used for regulating the flow of water, steam, or other media to the
prime mover for such purposes as starting, holding speed or load, or stopping.
66 Notching or jogging device functions to allow only a specified number of
operations of a given device or equipment, or a specified number of successive
operations within a given time of each other. It is also a device that functions to
energize a circuit periodically or for fractions of specified time intervals, or that
is used to permit intermittent acceleration or jogging of a machine at low speeds
for mechanical positioning.
67 Ac directional overcurrent relay is a relay that functions on a desired value
of ac overcurrent flowing in a predetermined direction.
68 Blocking relay is a relay that initiates a pilot signal for blocking of tripping
on external faults in a transmission line or in other apparatus under
predetermined conditions, or that cooperates with other devices to block
tripping or to block reclosing on an out-of-step condition or on power swings.
69 Permissive control device is generally, a two-position device that in one
position permits the closing of a circuit breaker, or the placing of an equipment
into operation, and in the other position prevents the circuit breaker or the
equipment from being operated.\
70 Rheostat is a variable resistance device used in an electric circuit which is
electrically operated or has other electrical accessories, such as auxiliary,
position, or limit switches.
71 Level switch is a switch that operates on given values, or on a given rate of
change, of level.
72 Dc circuit breaker is used to close and interrupt a dc power circuit under
normal conditions or to interrupt this circuit under fault or emergency
conditions.
73 Load-resistor contactor is used to shunt or insert a step of load limiting,
shifting, or indicating resistance in a power circuit, or to switch a space heater in
circuit, or to switch a light, or regenerative load resistor of a power rectifier or
other machine in and out of circuit.
74 Alarm relay is a relay other than an annunciator, as covered under device
function 30, that is used to operate, or that operates in connection with, a visual
or audible alarm.
of ac overcurrent flowing in a predetermined direction.
68 Blocking relay is a relay that initiates a pilot signal for blocking of tripping
on external faults in a transmission line or in other apparatus under
predetermined conditions, or that cooperates with other devices to block
tripping or to block reclosing on an out-of-step condition or on power swings.
69 Permissive control device is generally, a two-position device that in one
position permits the closing of a circuit breaker, or the placing of an equipment
into operation, and in the other position prevents the circuit breaker or the
equipment from being operated.\
70 Rheostat is a variable resistance device used in an electric circuit which is
electrically operated or has other electrical accessories, such as auxiliary,
position, or limit switches.
71 Level switch is a switch that operates on given values, or on a given rate of
change, of level.
72 Dc circuit breaker is used to close and interrupt a dc power circuit under
normal conditions or to interrupt this circuit under fault or emergency
conditions.
73 Load-resistor contactor is used to shunt or insert a step of load limiting,
shifting, or indicating resistance in a power circuit, or to switch a space heater in
circuit, or to switch a light, or regenerative load resistor of a power rectifier or
other machine in and out of circuit.
74 Alarm relay is a relay other than an annunciator, as covered under device
function 30, that is used to operate, or that operates in connection with, a visual
or audible alarm.
75 Position changing mechanism is a mechanism that is used for moving a
main device from one position to another in an equipment; for example, shifting
a removable circuit breaker unit to and from the connected, disconnected, and
test positions.
76 Dc overcurrent relay is a relay that functions when the current in a dc
circuit exceeds a given value.
77 Telemetering device is a transmitter used to generate and transmit to a
remote location an electrical signal representing a measured quantity, or a
receiver used to receive the electrical signal from a remote transmitter and
convert the signal to represent the original measured quantity.
78 Phase-angle measuring or out-of step protective relay is a relay that
functions at a predetermined phase angle between two voltages, or between two
currents, or between voltage and current.
79 Ac reclosing relay is a relay that controls the automatic reclosing and
locking out of an ac circuit interrupter.
80 Flow switch is a switch that operates on given values, or on a given rate of
change, of flow.
81 Frequency relay is a relay that responds to the frequency of an electrical
quantity, operating when the frequency or rate of change of frequency exceeds
or is less than a predetermined value.
82 Dc load-measuring reclosing relay is a relay that controls the automatic
closing and reclosing of a dc circuit interrupter, generally in response to load
circuit conditions.
83 Automatic selective control or transfer relay is a relay that operates to
select automatically between certain sources or conditions in an equipment or
that performs a transfer operation automatically.
main device from one position to another in an equipment; for example, shifting
a removable circuit breaker unit to and from the connected, disconnected, and
test positions.
76 Dc overcurrent relay is a relay that functions when the current in a dc
circuit exceeds a given value.
77 Telemetering device is a transmitter used to generate and transmit to a
remote location an electrical signal representing a measured quantity, or a
receiver used to receive the electrical signal from a remote transmitter and
convert the signal to represent the original measured quantity.
78 Phase-angle measuring or out-of step protective relay is a relay that
functions at a predetermined phase angle between two voltages, or between two
currents, or between voltage and current.
79 Ac reclosing relay is a relay that controls the automatic reclosing and
locking out of an ac circuit interrupter.
80 Flow switch is a switch that operates on given values, or on a given rate of
change, of flow.
81 Frequency relay is a relay that responds to the frequency of an electrical
quantity, operating when the frequency or rate of change of frequency exceeds
or is less than a predetermined value.
82 Dc load-measuring reclosing relay is a relay that controls the automatic
closing and reclosing of a dc circuit interrupter, generally in response to load
circuit conditions.
83 Automatic selective control or transfer relay is a relay that operates to
select automatically between certain sources or conditions in an equipment or
that performs a transfer operation automatically.
84 Operating mechanism is the complete electrical mechanism or
servomechanism, including the operating motor, solenoids, position switches,
etc., for a tap changer, induction regulator, or any similar piece of apparatus that
otherwise has no device function number.
85 Carrier or pilot-wire receiver relay is a relay that is operated or restrained
by a signal used in connection with carrier-current or dc pilot-wire fault
directional relaying.
86 Lockout relay is an electrically operated hand or electrically reset auxiliary
relay that is operated upon the occurrence of abnormal conditions to maintain
associated equipment or devices out of service until it is reset.
87 Differential protective relay is a protective relay that functions on a
percentage, or phase angle, or other quantitative difference between two
currents or some other electrical quantities.
88 Auxiliary motor or motor generator is a device used for operating
auxiliary equipment, such as pumps, blowers, exciters, rotating magnetic
amplifiers, etc.
89 Line switch is used as a disconnecting, load interrupter, or isolating switch
in an ac or dc power circuit. (This device function number is normally not
necessary unless the switch is electrically operated or has electrical accessories,
such as an auxiliary switch, a magnetic lock, etc.)
90 Regulating device functions to regulate a quantity or quantities, such as
voltage, current, power, speed, frequency, temperature, and load, at a certain
value or between certain (generally close) limits for machines, tie lines, or other
apparatus.
91 Voltage directional relay is a relay that operates when the voltage across an
open circuit breaker or contactor exceeds a given value in a given direction.
servomechanism, including the operating motor, solenoids, position switches,
etc., for a tap changer, induction regulator, or any similar piece of apparatus that
otherwise has no device function number.
85 Carrier or pilot-wire receiver relay is a relay that is operated or restrained
by a signal used in connection with carrier-current or dc pilot-wire fault
directional relaying.
86 Lockout relay is an electrically operated hand or electrically reset auxiliary
relay that is operated upon the occurrence of abnormal conditions to maintain
associated equipment or devices out of service until it is reset.
87 Differential protective relay is a protective relay that functions on a
percentage, or phase angle, or other quantitative difference between two
currents or some other electrical quantities.
88 Auxiliary motor or motor generator is a device used for operating
auxiliary equipment, such as pumps, blowers, exciters, rotating magnetic
amplifiers, etc.
89 Line switch is used as a disconnecting, load interrupter, or isolating switch
in an ac or dc power circuit. (This device function number is normally not
necessary unless the switch is electrically operated or has electrical accessories,
such as an auxiliary switch, a magnetic lock, etc.)
90 Regulating device functions to regulate a quantity or quantities, such as
voltage, current, power, speed, frequency, temperature, and load, at a certain
value or between certain (generally close) limits for machines, tie lines, or other
apparatus.
91 Voltage directional relay is a relay that operates when the voltage across an
open circuit breaker or contactor exceeds a given value in a given direction.
92 Voltage and power directional relay is a relay that permits or causes the
connection of two circuits when the voltage difference between them exceeds a
given value in a predetermined direction and causes these two circuits to be
disconnected from each other when the power flowing between them exceeds a
given value in the opposite direction.
93 Field-changing contactor functions to increase or decrease, in one step, the
value of field excitation on a machine.
BLACK START DG SET:-
Sometimes Bus 1 is failed While Bus 2 is working Then bus 1 is connected
to Bus 2 by using Bus Coupler and vice – versa.
When both Buses 1 and 2 are failed then Diesel Generator [DG Set] is
started to supply one GT which can be produce 106 MW.
For practice ,there is made a iland of providing power through only a Bus
meanwhile it is isolated from the Power Grid.
DG SET SPECIFICATION
Voltage=6.6 kV Power=3.4 MVA
GENERATOR
For excitation purpose Brushless exciter (DC) is used.
Air is compressed by using Compressor and diesel is used as fuel .
SPECIFICATION
3 phase Power= 4000 kW Apparent power=5000 kVA 50 Hz
V= 6.6 kV Maintain temp. =65
o
C
Compressor pressure= 34 bar
connection of two circuits when the voltage difference between them exceeds a
given value in a predetermined direction and causes these two circuits to be
disconnected from each other when the power flowing between them exceeds a
given value in the opposite direction.
93 Field-changing contactor functions to increase or decrease, in one step, the
value of field excitation on a machine.
BLACK START DG SET:-
Sometimes Bus 1 is failed While Bus 2 is working Then bus 1 is connected
to Bus 2 by using Bus Coupler and vice – versa.
When both Buses 1 and 2 are failed then Diesel Generator [DG Set] is
started to supply one GT which can be produce 106 MW.
For practice ,there is made a iland of providing power through only a Bus
meanwhile it is isolated from the Power Grid.
DG SET SPECIFICATION
Voltage=6.6 kV Power=3.4 MVA
GENERATOR
For excitation purpose Brushless exciter (DC) is used.
Air is compressed by using Compressor and diesel is used as fuel .
SPECIFICATION
3 phase Power= 4000 kW Apparent power=5000 kVA 50 Hz
V= 6.6 kV Maintain temp. =65
o
C
Compressor pressure= 34 bar
DIESEL ENGINE CAPACIT Y
O/P Power = 3000 kW Speed=1500 rpm
12 Piston 4 Stroke cycle
Engine capacity is more than Generator Capacity to avoid damaging of
generator winding .
DG SET Generator’s two phases connected to Bus 1 and Bus 2 whereas One
phase is connected to step down Transformer of 6.6 kV/440 V .
TRANSFORMER SPECIFICATION
3 phase 50 Hz Weight = 650 kg
Insulation = F Nominal current rating =8.75 , 131 A
Transformer is further connected to Machine circuit control (MCC)
MCC is connected to Auxiliary of DG SET
Auxiliary
Diesel cooling fans 5,4,3,2,1
Coupling
Spare
Pneumatic dictator compressor
Diesel battery charger
Diesel unloading pump
Diesel fuel transfer pump 1,2
Diesel pre lubricating pump
Diesel water circulating pump
Diesel air compressor 1,2
Diesel preheating 1,2,3
415/240 V transformer (protection)
Transformer is grounded through Resistance and CT which is called Air Gen.
Neutral Grounding .This is used for protection purpose from earth fault.
RESISTANCE SPECIFICATION
At 20
o
C = 30 Ω
O/P Power = 3000 kW Speed=1500 rpm
12 Piston 4 Stroke cycle
Engine capacity is more than Generator Capacity to avoid damaging of
generator winding .
DG SET Generator’s two phases connected to Bus 1 and Bus 2 whereas One
phase is connected to step down Transformer of 6.6 kV/440 V .
TRANSFORMER SPECIFICATION
3 phase 50 Hz Weight = 650 kg
Insulation = F Nominal current rating =8.75 , 131 A
Transformer is further connected to Machine circuit control (MCC)
MCC is connected to Auxiliary of DG SET
Auxiliary
Diesel cooling fans 5,4,3,2,1
Coupling
Spare
Pneumatic dictator compressor
Diesel battery charger
Diesel unloading pump
Diesel fuel transfer pump 1,2
Diesel pre lubricating pump
Diesel water circulating pump
Diesel air compressor 1,2
Diesel preheating 1,2,3
415/240 V transformer (protection)
Transformer is grounded through Resistance and CT which is called Air Gen.
Neutral Grounding .This is used for protection purpose from earth fault.
RESISTANCE SPECIFICATION
At 20
o
C = 30 Ω
TRANSFORMER
A Transformer is a static device consisting of a winding, or two or more
coupled windings, with or without a magnetic core, for inducing mutual
coupling between circuits.
When an alternating current flows in a conductor, a magnetic field exists around
the conductor. If another conductor is placed in the field created by the first
conductor such that the flux lines link the second conductor, then a voltage is
induced into the second conductor. The use of a magnetic field from one coil to
induce a voltage into a second coil is the principle on which transformer theory
and application is based.
Figure 5: A 220kV transformer
A Transformer is a static device consisting of a winding, or two or more
coupled windings, with or without a magnetic core, for inducing mutual
coupling between circuits.
When an alternating current flows in a conductor, a magnetic field exists around
the conductor. If another conductor is placed in the field created by the first
conductor such that the flux lines link the second conductor, then a voltage is
induced into the second conductor. The use of a magnetic field from one coil to
induce a voltage into a second coil is the principle on which transformer theory
and application is based.
Figure 5: A 220kV transformer
ANSI/IEEE Defines A Transformer as a static electrical device, involving no
continuously moving parts, used in electric power systems to transfer power
between circuits through the use of electromagnetic induction.
The Transformer is one of the most reliable pieces of electrical distribution
equipment. It has no moving parts, requires minimal maintenance, and is
capable of withstanding overloads, surges, faults, and physical abuse that may
damage or destroy other items in the circuit. Often, the electrical event that
burns up a motor, opens a circuit breaker, or blows a fuse has a subtle effect on
the transformer. Although the transformer may continue to operate as before,
repeat occurrences of such damaging electrical events, or lack of even minimal
maintenance can greatly accelerate the eventual failure of the transformer. The
fact that a transformer continues to operate satisfactorily in spite of neglect and
abuse is a testament to its durability. However, this durability is no excuse for
not providing the proper care.
Most of the effects of aging, faults, or abuse can be detected and corrected by a
comprehensive maintenance, inspection, and testing program.
Transformers are exclusively used in electric power systems to transfer power
by electromagnetic induction between circuits at the same frequency, usually
with changed values of voltage and current. There are numerous types of
transformers used in various applications including audio, radio, instrument, and
power. In KAWAS gas project power plant, we deal exclusively with power
transformer applications involving the transmission and distribution of electrical
power. Power transformers are used extensively by traditional electric utility
companies, power plants, and industrial plants. The term power transformer is
used to refer to those transformers used between the generator and the
distribution circuits, and these are usually rated at 220 kVA and above. Power
systems typically consist of a large number of generation locations, distribution
points, and interconnections within the system or with nearby systems, such as a
neighbouring utility. The complexity of the system leads to a variety of
transmission and distribution voltages. Power transformers must be used at each
of these points where there is a transition between voltage levels. Power
transformers are selected based on the application, with the emphasis toward
custom design being more apparent the larger the unit. Power transformers are
available for step-up operation, primarily used at the generator and referred to
as generator step-up (GSU)transformers, and for step-down operation, mainly
continuously moving parts, used in electric power systems to transfer power
between circuits through the use of electromagnetic induction.
The Transformer is one of the most reliable pieces of electrical distribution
equipment. It has no moving parts, requires minimal maintenance, and is
capable of withstanding overloads, surges, faults, and physical abuse that may
damage or destroy other items in the circuit. Often, the electrical event that
burns up a motor, opens a circuit breaker, or blows a fuse has a subtle effect on
the transformer. Although the transformer may continue to operate as before,
repeat occurrences of such damaging electrical events, or lack of even minimal
maintenance can greatly accelerate the eventual failure of the transformer. The
fact that a transformer continues to operate satisfactorily in spite of neglect and
abuse is a testament to its durability. However, this durability is no excuse for
not providing the proper care.
Most of the effects of aging, faults, or abuse can be detected and corrected by a
comprehensive maintenance, inspection, and testing program.
Transformers are exclusively used in electric power systems to transfer power
by electromagnetic induction between circuits at the same frequency, usually
with changed values of voltage and current. There are numerous types of
transformers used in various applications including audio, radio, instrument, and
power. In KAWAS gas project power plant, we deal exclusively with power
transformer applications involving the transmission and distribution of electrical
power. Power transformers are used extensively by traditional electric utility
companies, power plants, and industrial plants. The term power transformer is
used to refer to those transformers used between the generator and the
distribution circuits, and these are usually rated at 220 kVA and above. Power
systems typically consist of a large number of generation locations, distribution
points, and interconnections within the system or with nearby systems, such as a
neighbouring utility. The complexity of the system leads to a variety of
transmission and distribution voltages. Power transformers must be used at each
of these points where there is a transition between voltage levels. Power
transformers are selected based on the application, with the emphasis toward
custom design being more apparent the larger the unit. Power transformers are
available for step-up operation, primarily used at the generator and referred to
as generator step-up (GSU)transformers, and for step-down operation, mainly
used to feed distribution circuits. Power transformers are available as single-
phase or three-phase apparatus.
CONSTRUCTION OF TRANSFORMER : -
Basically a transformer consists of two inductive windings and a laminated steel
core. The coils are insulated from each other as well as from the steel core. A
transformer may also consist of a container for winding and core assembly
(called as tank), suitable bushings to take our the terminals, oil conservator to
provide oil in the transformer tank for cooling purposes etc. The figure at left
illustrates the basic construction of a transformer.
In all types of transformers, core is constructed by assembling (stacking)
laminated sheets of steel, with minimum air-gap between them (to achieve
continuous magnetic path). The steel used is having high silicon content and
sometimes heat treated, to provide high permeability and low hysteresis loss.
Laminated sheets of steel are used to reduce eddy current loss. The sheets are
cut in the shape as E,I and L. To avoid high reluctance at joints, laminations are
stacked by alternating the sides of joint. That is, if joints of first sheet assembly
are at front face, the joints of following assemble are kept at back face.
phase or three-phase apparatus.
CONSTRUCTION OF TRANSFORMER : -
Basically a transformer consists of two inductive windings and a laminated steel
core. The coils are insulated from each other as well as from the steel core. A
transformer may also consist of a container for winding and core assembly
(called as tank), suitable bushings to take our the terminals, oil conservator to
provide oil in the transformer tank for cooling purposes etc. The figure at left
illustrates the basic construction of a transformer.
In all types of transformers, core is constructed by assembling (stacking)
laminated sheets of steel, with minimum air-gap between them (to achieve
continuous magnetic path). The steel used is having high silicon content and
sometimes heat treated, to provide high permeability and low hysteresis loss.
Laminated sheets of steel are used to reduce eddy current loss. The sheets are
cut in the shape as E,I and L. To avoid high reluctance at joints, laminations are
stacked by alternating the sides of joint. That is, if joints of first sheet assembly
are at front face, the joints of following assemble are kept at back face.
TYPES OF TRANSFORMER
Transformers can be classified on different basis, like types of construction,
types of cooling etc.
(A) On the basis of construction, transformers can be classified
into two types as;
(i) Core type transformer
(ii) Shell type transformer
(i) (I) Core Type Transformer
In core type transformer, windings are cylindrical former wound, mounted on
the core limbs as shown in the figure above. The cylindrical coils have different
layers and each layer is insulated from each other. Materials like paper, cloth or
mica can be used for insulation. Low voltage windings are placed nearer to the
core, as they are easier to insulate.
(ii) (II) Shell Type Transformer
The coils are former wound and mounted in layers stacked with insulation
between them. A shell type transformer may have simple rectangular form (as
shown in above fig), or it may have a distributed form.
Transformers can be classified on different basis, like types of construction,
types of cooling etc.
(A) On the basis of construction, transformers can be classified
into two types as;
(i) Core type transformer
(ii) Shell type transformer
(i) (I) Core Type Transformer
In core type transformer, windings are cylindrical former wound, mounted on
the core limbs as shown in the figure above. The cylindrical coils have different
layers and each layer is insulated from each other. Materials like paper, cloth or
mica can be used for insulation. Low voltage windings are placed nearer to the
core, as they are easier to insulate.
(ii) (II) Shell Type Transformer
The coils are former wound and mounted in layers stacked with insulation
between them. A shell type transformer may have simple rectangular form (as
shown in above fig), or it may have a distributed form.
(B) On the basis of their purpose
1. Step up transformer: Voltage increases (with subsequent decrease in
current) at secondary.
2. Step down transformer: Voltage decreases (with subsequent increase in
current) at secondary.
(C) On the basis of type of supply
1. Single phase transformer
2. Three phase transformer
(D) On the basis of their use
1. Power transformer: Used in transmission network, high rating
2. Distribution transformer: Used in distribution network, comparatively
lower rating than that of power transformers.
3. Autotransformer: Transformer in which part of the winding is common to
both primary and secondary circuits, leading to increased efficiency,
smaller size, and a higher degree of voltage regulation.
4. Capacitor voltage transformer: Transformer in which capacitor divider is
used to reduce high voltage before application to the primary winding.
5. Phase angle regulating transformer:- A specialised transformer used to
control the flow of real power on three-phase electricity transmission
networks.
6. Scott-T transformer:- Transformer used for phase transformation from
three-phase to two-phase and vice versa.
[96]
7. Poly phase transformer:- Any transformer with more than one phase.
8. Zigzag transformer:- Special-purpose transformer with a zigzag or
"interconnected star" winding connection.
9. Grounding transformer:- Transformer used for grounding three-phase
circuits to create a neutral in a three wire system, using a Y-delta
transformer, or more commonly, a zigzag grounding winding.
10. Leakage transformer: -Transformer that has loosely coupled windings.
11. Resonant transformer: -Transformer that uses resonance to generate a
high secondary voltage.
12. Audio transformer:- Transformer used in audio equipment.
13. Output transformer: -Transformer used to match the output of a valve
amplifier to its load.
1. Step up transformer: Voltage increases (with subsequent decrease in
current) at secondary.
2. Step down transformer: Voltage decreases (with subsequent increase in
current) at secondary.
(C) On the basis of type of supply
1. Single phase transformer
2. Three phase transformer
(D) On the basis of their use
1. Power transformer: Used in transmission network, high rating
2. Distribution transformer: Used in distribution network, comparatively
lower rating than that of power transformers.
3. Autotransformer: Transformer in which part of the winding is common to
both primary and secondary circuits, leading to increased efficiency,
smaller size, and a higher degree of voltage regulation.
4. Capacitor voltage transformer: Transformer in which capacitor divider is
used to reduce high voltage before application to the primary winding.
5. Phase angle regulating transformer:- A specialised transformer used to
control the flow of real power on three-phase electricity transmission
networks.
6. Scott-T transformer:- Transformer used for phase transformation from
three-phase to two-phase and vice versa.
[96]
7. Poly phase transformer:- Any transformer with more than one phase.
8. Zigzag transformer:- Special-purpose transformer with a zigzag or
"interconnected star" winding connection.
9. Grounding transformer:- Transformer used for grounding three-phase
circuits to create a neutral in a three wire system, using a Y-delta
transformer, or more commonly, a zigzag grounding winding.
10. Leakage transformer: -Transformer that has loosely coupled windings.
11. Resonant transformer: -Transformer that uses resonance to generate a
high secondary voltage.
12. Audio transformer:- Transformer used in audio equipment.
13. Output transformer: -Transformer used to match the output of a valve
amplifier to its load.
14. Pulse transformer: -Specialized small-signal transformer used to transmit
digital signaling while providing electrical isolation, commonly used
in Ethernet computer networks as 10BASE-T, 100BASE-T and
1000BASE-T.
15. Instrument transformer:- Used in relay and protection purpose in
different instruments in industries
Current transformer (CT)
Potential transformer (PT)
(E) On the basis of cooling employed
1. Oil-filled self cooled type
2. Oil-filled water cooled type
3. Air blast type (air cooled)
WORKING PRINCIPLE OF TRANSFORMER: -
The working principle of transformer is very simple. It depends upon Faraday's
law of electromagnetic induction. Mutual induction between two or more
winding is responsible for transformation action in an electrical transformer.
Faraday's Laws of Electromagnetic Induction
According to these Faraday's laws, "Rate of change of flux linkage with respect
to time is directly proportional to the induced EMF in a conductor or coil".
Basic Theory of Transformer
X’mer have one winding which is supplied by an alternating electrical source.
The alternating current through the winding produces a continually changing
flux or alternating flux that surrounds the winding. If any other winding is
brought nearer to the previous one, obviously some portion of this flux will link
with the second. As this flux is continually changing in its amplitude and
direction, there must be a change in flux linkage in the second winding or coil.
According to Faraday's law of electromagnetic induction, there must be an EMF
induced in the second. If the circuit of the later winding is closed, there must be
a current flowing through it. This is the simplest form of an electrical power
transformer, and this is the most basic of working principle of transformer.
digital signaling while providing electrical isolation, commonly used
in Ethernet computer networks as 10BASE-T, 100BASE-T and
1000BASE-T.
15. Instrument transformer:- Used in relay and protection purpose in
different instruments in industries
Current transformer (CT)
Potential transformer (PT)
(E) On the basis of cooling employed
1. Oil-filled self cooled type
2. Oil-filled water cooled type
3. Air blast type (air cooled)
WORKING PRINCIPLE OF TRANSFORMER: -
The working principle of transformer is very simple. It depends upon Faraday's
law of electromagnetic induction. Mutual induction between two or more
winding is responsible for transformation action in an electrical transformer.
Faraday's Laws of Electromagnetic Induction
According to these Faraday's laws, "Rate of change of flux linkage with respect
to time is directly proportional to the induced EMF in a conductor or coil".
Basic Theory of Transformer
X’mer have one winding which is supplied by an alternating electrical source.
The alternating current through the winding produces a continually changing
flux or alternating flux that surrounds the winding. If any other winding is
brought nearer to the previous one, obviously some portion of this flux will link
with the second. As this flux is continually changing in its amplitude and
direction, there must be a change in flux linkage in the second winding or coil.
According to Faraday's law of electromagnetic induction, there must be an EMF
induced in the second. If the circuit of the later winding is closed, there must be
a current flowing through it. This is the simplest form of an electrical power
transformer, and this is the most basic of working principle of transformer.
Whenever we apply alternating current to an electric coil, there will be an
alternating flux surrounding that coil. Now if we bring another coil near the first
one, there will be an alternating flux linkage with that second coil. As the flux is
alternating, there will be obviously a rate of change in flux linkage with respect
to time in the second coil. Naturally emf will be induced in it as per Faraday's
law of electromagnetic induction. This is the most basic concept of the theory of
transformer.
The winding which takes electrical power from the source, is known as the
primary winding of a transformer. Here in our above example, it is first
winding.
The winding which gives the desired output voltage due to mutual induction in
the transformer is commonly known as the secondary winding of the
alternating flux surrounding that coil. Now if we bring another coil near the first
one, there will be an alternating flux linkage with that second coil. As the flux is
alternating, there will be obviously a rate of change in flux linkage with respect
to time in the second coil. Naturally emf will be induced in it as per Faraday's
law of electromagnetic induction. This is the most basic concept of the theory of
transformer.
The winding which takes electrical power from the source, is known as the
primary winding of a transformer. Here in our above example, it is first
winding.
The winding which gives the desired output voltage due to mutual induction in
the transformer is commonly known as the secondary winding of the
transformer. Here in our example, it is second winding.
The form mentioned above of a transformer is theoretically possible but not
practically, because in open air very tiny portion of the flux of the first winding
will link with second; so the current that flows through the closed circuit of
later, will be so small in amount that it will be difficult to measure.
The rate of change of flux linkage depends upon the amount of linked flux with
the second winding. So, almost all flux of primary winding should link to the
secondary winding. This is effectively and efficiently done by placing one low
reluctance path common to both of the winding. This low reluctance path is core
of transformer, through which the maximum number of flux produced by the
primary is passed through and linked with the secondary winding. This is the
most basic theory of transformer.
CONSTRUCTION :-
The form mentioned above of a transformer is theoretically possible but not
practically, because in open air very tiny portion of the flux of the first winding
will link with second; so the current that flows through the closed circuit of
later, will be so small in amount that it will be difficult to measure.
The rate of change of flux linkage depends upon the amount of linked flux with
the second winding. So, almost all flux of primary winding should link to the
secondary winding. This is effectively and efficiently done by placing one low
reluctance path common to both of the winding. This low reluctance path is core
of transformer, through which the maximum number of flux produced by the
primary is passed through and linked with the secondary winding. This is the
most basic theory of transformer.
CONSTRUCTION :-
COOLING
Cutaway view of liquid-immersed construction transformer. The conservator
(reservoir) at top provides liquid-to-atmosphere isolation as coolant level and
temperature changes. The walls and fins provide required heat dissipation
balance.
It is a rule of thumb that the life expectancy of electrical insulation is halved for
about every 7 °C to 10 °C increase in operating temperature (an instance of the
application of the Arrhenius equation).
Small dry-type and liquid-immersed transformers are often self-cooled by
natural convection and radiation heat dissipation. As power ratings increase,
transformers are often cooled by forced-air cooling, forced-oil cooling, water-
cooling, or combinations of these. Large transformers are filled
with transformer oil that both cools and insulates the windings. Transformer oil
is a highly refined mineral oil that cools the windings and insulation by
circulating within the transformer tank. The mineral oil and paper insulation
system has been extensively studied and used for more than 100 years. It is
estimated that 50% of power transformers will survive 50 years of use, that the
average age of failure of power transformers is about 10 to 15 years, and that
about 30% of power transformer failures are due to insulation and overloading
failures. Prolonged operation at elevated temperature degrades insulating
properties of winding insulation and dielectric coolant, which not only shortens
transformer life but can ultimately lead to catastrophic transformer failure. With
a great body of empirical study as a guide, transformer oil
testing including dissolved gas analysis provides valuable maintenance
information. This underlines the need to monitor, model, forecast and manage
oil and winding conductor insulation temperature conditions under varying,
possibly difficult, power loading conditions.
Building regulations in many jurisdictions require indoor liquid-filled
transformers to either use dielectric fluids that are less flammable than oil, or be
Cutaway view of liquid-immersed construction transformer. The conservator
(reservoir) at top provides liquid-to-atmosphere isolation as coolant level and
temperature changes. The walls and fins provide required heat dissipation
balance.
It is a rule of thumb that the life expectancy of electrical insulation is halved for
about every 7 °C to 10 °C increase in operating temperature (an instance of the
application of the Arrhenius equation).
Small dry-type and liquid-immersed transformers are often self-cooled by
natural convection and radiation heat dissipation. As power ratings increase,
transformers are often cooled by forced-air cooling, forced-oil cooling, water-
cooling, or combinations of these. Large transformers are filled
with transformer oil that both cools and insulates the windings. Transformer oil
is a highly refined mineral oil that cools the windings and insulation by
circulating within the transformer tank. The mineral oil and paper insulation
system has been extensively studied and used for more than 100 years. It is
estimated that 50% of power transformers will survive 50 years of use, that the
average age of failure of power transformers is about 10 to 15 years, and that
about 30% of power transformer failures are due to insulation and overloading
failures. Prolonged operation at elevated temperature degrades insulating
properties of winding insulation and dielectric coolant, which not only shortens
transformer life but can ultimately lead to catastrophic transformer failure. With
a great body of empirical study as a guide, transformer oil
testing including dissolved gas analysis provides valuable maintenance
information. This underlines the need to monitor, model, forecast and manage
oil and winding conductor insulation temperature conditions under varying,
possibly difficult, power loading conditions.
Building regulations in many jurisdictions require indoor liquid-filled
transformers to either use dielectric fluids that are less flammable than oil, or be
installed in fire-resistant rooms. Air-cooled dry transformers can be more
economical where they eliminate the cost of a fire-resistant transformer room.
The tank of liquid filled transformers often has radiators through which the
liquid coolant circulates by natural convection or fins. Some large transformers
employ electric fans for forced-air cooling, pumps for forced-liquid cooling, or
have heat exchangers for water-cooling. An oil-immersed transformer may be
equipped with a Buchholz relay, which, depending on severity of gas
accumulation due to internal arcing, is used to either alarm or de-energize the
transformer. Oil-immersed transformer installations usually include fire
protection measures such as walls, oil containment, and fire-suppression
sprinkler systems.
Polychlorinated biphenyls have properties that once favored their use as
a dielectric coolant, though concerns over their environmental persistence led to
a widespread ban on their use. Today, non-toxic, stable silicone-based oils,
or fluorinated hydrocarbons may be used where the expense of a fire-resistant
liquid offsets additional building cost for a transformer vault. PCBs for new
equipment were banned in 1981 and in 2000 for use in existing equipment in
United Kingdom
.
Legislation enacted in Canada between 1977 and 1985
essentially bans PCB use in transformers manufactured in or imported into the
country after 1980, the maximum allowable level of PCB contamination in
existing mineral oil transformers being 50 ppm .
Some transformers, instead of being liquid-filled, have their windings enclosed
in sealed, pressurized tanks and cooled by nitrogen or sulfur hexafluoride gas.
Experimental power transformers in the 500‐to‐1,000 kVA range have been
built with liquid nitrogen or helium cooled superconducting windings, which
eliminates winding losses without affecting core losses.
INSULATION DRYING
Construction of oil-filled transformers requires that the insulation covering the
windings be thoroughly dried of residual moisture before the oil is introduced.
Drying is carried out at the factory, and may also be required as a field service.
Drying may be done by circulating hot air around the core, by circulating
externally heated transformer oil, or by vapour-phase drying (VPD) where an
evaporated solvent transfers heat by condensation on the coil and core. The
VPD process most often uses kerosene as the heat exchanging fluid. In addition
to decreasing the moisture content in the insulation, the kerosene acts as a
cleaning solvent which takes out any dust and dirt from the insulation surfaces.
Compared to a conventional hot air drying process, the vapour-phase drying
process decreases the drying time by 40% to 50%.
For small transformers, resistance heating by injection of current into the
windings is used. The heating can be controlled very well, and it is energy
economical where they eliminate the cost of a fire-resistant transformer room.
The tank of liquid filled transformers often has radiators through which the
liquid coolant circulates by natural convection or fins. Some large transformers
employ electric fans for forced-air cooling, pumps for forced-liquid cooling, or
have heat exchangers for water-cooling. An oil-immersed transformer may be
equipped with a Buchholz relay, which, depending on severity of gas
accumulation due to internal arcing, is used to either alarm or de-energize the
transformer. Oil-immersed transformer installations usually include fire
protection measures such as walls, oil containment, and fire-suppression
sprinkler systems.
Polychlorinated biphenyls have properties that once favored their use as
a dielectric coolant, though concerns over their environmental persistence led to
a widespread ban on their use. Today, non-toxic, stable silicone-based oils,
or fluorinated hydrocarbons may be used where the expense of a fire-resistant
liquid offsets additional building cost for a transformer vault. PCBs for new
equipment were banned in 1981 and in 2000 for use in existing equipment in
United Kingdom
.
Legislation enacted in Canada between 1977 and 1985
essentially bans PCB use in transformers manufactured in or imported into the
country after 1980, the maximum allowable level of PCB contamination in
existing mineral oil transformers being 50 ppm .
Some transformers, instead of being liquid-filled, have their windings enclosed
in sealed, pressurized tanks and cooled by nitrogen or sulfur hexafluoride gas.
Experimental power transformers in the 500‐to‐1,000 kVA range have been
built with liquid nitrogen or helium cooled superconducting windings, which
eliminates winding losses without affecting core losses.
INSULATION DRYING
Construction of oil-filled transformers requires that the insulation covering the
windings be thoroughly dried of residual moisture before the oil is introduced.
Drying is carried out at the factory, and may also be required as a field service.
Drying may be done by circulating hot air around the core, by circulating
externally heated transformer oil, or by vapour-phase drying (VPD) where an
evaporated solvent transfers heat by condensation on the coil and core. The
VPD process most often uses kerosene as the heat exchanging fluid. In addition
to decreasing the moisture content in the insulation, the kerosene acts as a
cleaning solvent which takes out any dust and dirt from the insulation surfaces.
Compared to a conventional hot air drying process, the vapour-phase drying
process decreases the drying time by 40% to 50%.
For small transformers, resistance heating by injection of current into the
windings is used. The heating can be controlled very well, and it is energy
efficient. The method is called low-frequency heating (LFH) since the current
used is at a much lower frequency than that of the power grid, which is
normally 50 or 60 Hz. A lower frequency reduces the effect of inductance, so
the voltage required can be reduced. The LFH drying method is also used for
service of older transformers.
BUSHINGS
Larger transformers are provided with high-voltage insulated bushings made of
polymers or porcelain. A large bushing can be a complex structure since it must
provide careful control of the electric field gradient without letting the
transformer leak oil.
WINDING
The windings consist of the current-carrying conductors wound around the
sections of the core, and these must be properly insulated, supported, and cooled
to withstand operational and test conditions. Copper and aluminum are the
primary materials used as conductors in power-transformer windings. While
aluminum is lighter and generally less expensive than copper, a larger cross
section of aluminum conductor must be used to carry a current with similar
performance as copper. Copper has higher mechanical strength and is used
almost exclusively in all but the smaller size ranges, where aluminum
conductors may be perfectly acceptable. In cases where extreme forces are
encountered, materials such as silver-bearing copper can be used for even
greater strength. The conductors used in power transformers are typically
stranded with a rectangular cross section, although some transformers at the
lowest ratings may use sheet or foil conductors. Multiple strands can be wound
in parallel and joined together at the ends of the winding, in which case it is
necessary to transpose the strands at various points throughout the winding to
prevent circulating currents around the loop(s) created by joining the strands at
the ends. Individual strands may be subjected to differences in the flux field due
to their respective positions within the winding, which create differences in
voltages between the strands and drive circulating currents through the
conductor loops. Proper transposition of the strands cancels out these voltage
differences and eliminates or greatly reduces the circulating currents. A
variation of this technique, involving many rectangular conductor strands
combined into a cable, is called continuously transposed cable (CTC). In core-
form transformers, the windings are usually arranged concentrically around the
core leg, which shows a winding being lowered over another winding already
on the core leg of a three- phase transformer. Shell-form transformers use a
similar concentric arrangement or an interleaved arrangement.
used is at a much lower frequency than that of the power grid, which is
normally 50 or 60 Hz. A lower frequency reduces the effect of inductance, so
the voltage required can be reduced. The LFH drying method is also used for
service of older transformers.
BUSHINGS
Larger transformers are provided with high-voltage insulated bushings made of
polymers or porcelain. A large bushing can be a complex structure since it must
provide careful control of the electric field gradient without letting the
transformer leak oil.
WINDING
The windings consist of the current-carrying conductors wound around the
sections of the core, and these must be properly insulated, supported, and cooled
to withstand operational and test conditions. Copper and aluminum are the
primary materials used as conductors in power-transformer windings. While
aluminum is lighter and generally less expensive than copper, a larger cross
section of aluminum conductor must be used to carry a current with similar
performance as copper. Copper has higher mechanical strength and is used
almost exclusively in all but the smaller size ranges, where aluminum
conductors may be perfectly acceptable. In cases where extreme forces are
encountered, materials such as silver-bearing copper can be used for even
greater strength. The conductors used in power transformers are typically
stranded with a rectangular cross section, although some transformers at the
lowest ratings may use sheet or foil conductors. Multiple strands can be wound
in parallel and joined together at the ends of the winding, in which case it is
necessary to transpose the strands at various points throughout the winding to
prevent circulating currents around the loop(s) created by joining the strands at
the ends. Individual strands may be subjected to differences in the flux field due
to their respective positions within the winding, which create differences in
voltages between the strands and drive circulating currents through the
conductor loops. Proper transposition of the strands cancels out these voltage
differences and eliminates or greatly reduces the circulating currents. A
variation of this technique, involving many rectangular conductor strands
combined into a cable, is called continuously transposed cable (CTC). In core-
form transformers, the windings are usually arranged concentrically around the
core leg, which shows a winding being lowered over another winding already
on the core leg of a three- phase transformer. Shell-form transformers use a
similar concentric arrangement or an interleaved arrangement.
With an interleaved arrangement, individual coils are stacked, separated by
insulating barriers and cooling ducts. The coils are typically connected with the
inside of one coil connected to the inside of an adjacent coil and, similarly, the
outside of one coil connected to the outside of an adjacent coil. Sets of coils are
assembled into groups, which then form the primary or secondary winding.
When considering concentric windings, it is generally understood that circular
windings have inherently higher mechanical strength than rectangular windings,
whereas rectangular coils can have lower associated material and labour costs.
Rectangular windings permit a more efficient use of space, but their use is
limited to small power transformers and the lower range of medium- power
transformers, where the internal forces are not extremely high. As the rating
increases, the forces significantly increase, and there is need for added strength
in the windings, so circular coils, or shell-form construction, is used. In some
special cases, elliptically shaped windings are used. Concentric coils are
typically wound over cylinders with spacers attached so as to form a duct
between the conductors and the cylinder. As previously mentioned, the flow of
liquid through the windings can be based solely on natural convection, or the
flow can be somewhat controlled through the use of strategically placed barriers
within the winding. This concept is sometimes referred to as guided liquid flow.
A variety of different types of windings have been used in power transformers
through the years. Coils can be wound in an upright, vertical orientation, as is
necessary with larger, heavier coils; or they can be wound horizontally and
placed upright upon completion. As mentioned previously, the type of winding
depends on the transformer rating as well as the core construction. Several of
the more common winding types are discussed further.
1. Pancake Windings
Several types of windings are commonly referred to as “pancake” windings due
to the arrangement of conductors into discs. However, the term most often
refers to a coil type that is used almost exclusively in shell-form transformers.
The conductors are wound around a rectangular form, with the widest face of
the conductor oriented either horizontally or vertically. This type of winding
lends itself to the interleaved arrangement previously discussed.
2. Disc Windings
A disc winding can involve a single strand or several strands of insulated
conductors wound in a series of parallel discs of horizontal orientation, with the
discs connected at either the inside or outside as a crossover point. Each disc
comprises multiple turns wound over other turns, with the crossovers alternating
between inside and outside. Most windings of 25-kV class and above used in
core form transformers are disc type. Given the high voltages involved in test
insulating barriers and cooling ducts. The coils are typically connected with the
inside of one coil connected to the inside of an adjacent coil and, similarly, the
outside of one coil connected to the outside of an adjacent coil. Sets of coils are
assembled into groups, which then form the primary or secondary winding.
When considering concentric windings, it is generally understood that circular
windings have inherently higher mechanical strength than rectangular windings,
whereas rectangular coils can have lower associated material and labour costs.
Rectangular windings permit a more efficient use of space, but their use is
limited to small power transformers and the lower range of medium- power
transformers, where the internal forces are not extremely high. As the rating
increases, the forces significantly increase, and there is need for added strength
in the windings, so circular coils, or shell-form construction, is used. In some
special cases, elliptically shaped windings are used. Concentric coils are
typically wound over cylinders with spacers attached so as to form a duct
between the conductors and the cylinder. As previously mentioned, the flow of
liquid through the windings can be based solely on natural convection, or the
flow can be somewhat controlled through the use of strategically placed barriers
within the winding. This concept is sometimes referred to as guided liquid flow.
A variety of different types of windings have been used in power transformers
through the years. Coils can be wound in an upright, vertical orientation, as is
necessary with larger, heavier coils; or they can be wound horizontally and
placed upright upon completion. As mentioned previously, the type of winding
depends on the transformer rating as well as the core construction. Several of
the more common winding types are discussed further.
1. Pancake Windings
Several types of windings are commonly referred to as “pancake” windings due
to the arrangement of conductors into discs. However, the term most often
refers to a coil type that is used almost exclusively in shell-form transformers.
The conductors are wound around a rectangular form, with the widest face of
the conductor oriented either horizontally or vertically. This type of winding
lends itself to the interleaved arrangement previously discussed.
2. Disc Windings
A disc winding can involve a single strand or several strands of insulated
conductors wound in a series of parallel discs of horizontal orientation, with the
discs connected at either the inside or outside as a crossover point. Each disc
comprises multiple turns wound over other turns, with the crossovers alternating
between inside and outside. Most windings of 25-kV class and above used in
core form transformers are disc type. Given the high voltages involved in test
and operation, particular attention is required to avoid high stresses between
discs and turns near the end of the winding when subjected to transient voltage
surges. Numerous techniques have been developed to ensure an acceptable
voltage distribution along the winding under these conditions.
PROTECTION COMPONENTS OF TRANSFORMER: -
Oil Transformer protection
The power transformer protection is realized with two different kinds of
devices, namely the devices that are measuring the electrical
quantities affecting the transformer through instrument transformers and the
devices that are indicating the status of the physical quantities at the
transformer it self. An example of the former could be current-based
differential protection and of the latter oil temperature monitoring.
Protection Devices:-
The following discusses protection devices typically delivered as a part of the
power transformer delivery.
1. Buchholz (Gas) Relay
2. Pressure Relay
3. Oil Level Monitor Device
4. Winding Thermometer
The power transformer protection as a whole and the utilization of the below
presented protection devices are not discussed here.
1. Buchholz (Gas) Relay:-
The Buchholz protection is a mechanical fault detector for electrical
faults in oil-immersed transformers. The Buchholz (gas) relay is placed in the
piping between the transformer main tank and the oil conservator. The
conservator pipe must be inclined slightly for reliable operation .Often there
is a bypass pipe that makes it possible to take the Buchholz relay out of
service.
discs and turns near the end of the winding when subjected to transient voltage
surges. Numerous techniques have been developed to ensure an acceptable
voltage distribution along the winding under these conditions.
PROTECTION COMPONENTS OF TRANSFORMER: -
Oil Transformer protection
The power transformer protection is realized with two different kinds of
devices, namely the devices that are measuring the electrical
quantities affecting the transformer through instrument transformers and the
devices that are indicating the status of the physical quantities at the
transformer it self. An example of the former could be current-based
differential protection and of the latter oil temperature monitoring.
Protection Devices:-
The following discusses protection devices typically delivered as a part of the
power transformer delivery.
1. Buchholz (Gas) Relay
2. Pressure Relay
3. Oil Level Monitor Device
4. Winding Thermometer
The power transformer protection as a whole and the utilization of the below
presented protection devices are not discussed here.
1. Buchholz (Gas) Relay:-
The Buchholz protection is a mechanical fault detector for electrical
faults in oil-immersed transformers. The Buchholz (gas) relay is placed in the
piping between the transformer main tank and the oil conservator. The
conservator pipe must be inclined slightly for reliable operation .Often there
is a bypass pipe that makes it possible to take the Buchholz relay out of
service.
The Buchholz protection is a fast and sensitive fault detector. It works
independent of the number of transformer windings, tap changer position and
instrument transformers. If the tap changer is of the on-tank (container) type,
having its own oil enclosure with oil conservator, there is a dedicated
Buchholz relay for the tap changer .A typical Buchholz protection comprises
a pivoted float (F) and a pivoted vane (V) as shown in Figure 1. The float
carries one mercury switch and the vane also carries another mercury switch.
Normally, the casing is filled with oil and the mercury switches are open.
When minor fault occurs…
Here is assumed that a minor fault occurs within the transformer. Gases
produced by minor faults rise from the fault location to the top of the
transformer. Then the gas bubbles pass up the piping to the conservator. The
gas bubbles will be tapped in the casing of the Buchholz protection.This
means that the gas replaces the oil in the casing. As the oil level falls, the float
(F) will follow and the mercury switch tilts and closes an alarm circuit.
When major fault occurs…
It is also assumed that a major fault, either to earth of between phases or
windings, occurs within the transformer. Such faults rapidly produce large
volumes of gas (more than 50 cm3/(kWs) and oil vapour which cannot escape
independent of the number of transformer windings, tap changer position and
instrument transformers. If the tap changer is of the on-tank (container) type,
having its own oil enclosure with oil conservator, there is a dedicated
Buchholz relay for the tap changer .A typical Buchholz protection comprises
a pivoted float (F) and a pivoted vane (V) as shown in Figure 1. The float
carries one mercury switch and the vane also carries another mercury switch.
Normally, the casing is filled with oil and the mercury switches are open.
When minor fault occurs…
Here is assumed that a minor fault occurs within the transformer. Gases
produced by minor faults rise from the fault location to the top of the
transformer. Then the gas bubbles pass up the piping to the conservator. The
gas bubbles will be tapped in the casing of the Buchholz protection.This
means that the gas replaces the oil in the casing. As the oil level falls, the float
(F) will follow and the mercury switch tilts and closes an alarm circuit.
When major fault occurs…
It is also assumed that a major fault, either to earth of between phases or
windings, occurs within the transformer. Such faults rapidly produce large
volumes of gas (more than 50 cm3/(kWs) and oil vapour which cannot escape
.They therefore produce a steep build up of pressure and displace oil. This sets
up a rapid flow from the transformer towards the conservator. The vane (V)
responds to high oil and gas flow in the pipe to the conservator. In this case,
the mercury switch closes a trip circuit. The operating time of the trip contact
depends on the location of the fault and the magnitude of the fault current
.The gas accumulator relay also provides a long-term accumulation of
gasses associated with overheating of various parts of the transformer
conductor and insulation systems. This will detect fault sources in their early
stages and prevent significant damage. When the transformer is first put into
service, the air trapped in the windings may give unnecessary alarm signals. It
is customary to remove the air in the power transformers by vacuum treatment
during the filling of the transformer tank with oil .The gas accumulated
without this treatment will, of course, be air, which can be confirmed by
seeing that it is not inflammable.
2. Pressure Relay
Many power transformers with an on-tank-type tap changer have a pressure
protection for the separate tap changer oil compartment. This
protection detects a sudden rate-of-increase of pressure inside the tap
changer oil enclosure.
Figure shows the principle of a pressure relay.
When the pressure in front of the piston exceeds the counter force of the
spring, the piston will move operating the switching contacts. The micro
up a rapid flow from the transformer towards the conservator. The vane (V)
responds to high oil and gas flow in the pipe to the conservator. In this case,
the mercury switch closes a trip circuit. The operating time of the trip contact
depends on the location of the fault and the magnitude of the fault current
.The gas accumulator relay also provides a long-term accumulation of
gasses associated with overheating of various parts of the transformer
conductor and insulation systems. This will detect fault sources in their early
stages and prevent significant damage. When the transformer is first put into
service, the air trapped in the windings may give unnecessary alarm signals. It
is customary to remove the air in the power transformers by vacuum treatment
during the filling of the transformer tank with oil .The gas accumulated
without this treatment will, of course, be air, which can be confirmed by
seeing that it is not inflammable.
2. Pressure Relay
Many power transformers with an on-tank-type tap changer have a pressure
protection for the separate tap changer oil compartment. This
protection detects a sudden rate-of-increase of pressure inside the tap
changer oil enclosure.
Figure shows the principle of a pressure relay.
When the pressure in front of the piston exceeds the counter force of the
spring, the piston will move operating the switching contacts. The micro
switch inside the switching unit is hermetically sealed and pressurized with
nitrogen gas.The simplest form of pressure relief device is the widely
used frangible disk. The surge of oil caused by a heavy internal fault bursts
the disk and allows the oil to discharge rapidly. Relieving and limiting the
pressure rise prevent explosive rupture of the tank and consequent fire.Also, if
used, the separate tap changer oil enclosure can be fitted with a pressure relief
device. The pressure relief device can be fitted with contact unit(s) to provide
a signal for circuit breaker(s) tripping circuits. A drawback of the frangible
disk is that the oil remaining in the tank is left exposed to the atmosphere
after a rupture. This is avoided in a more effective device, the pressure relief
valve, which opens to allow the discharge of oil if the pressure exceeds the
pre-adjusted limit. If the abnormal pressure is relatively high, this spring-
controlled valve can operate within a few milliseconds and provide fast
tripping when suitable contacts are fitted. The valve closes automatically as
the internal pressure falls below a critical level.
3. Oil Level Monitor Device
Transformers with oil conservator(s) (expansion tank) often have an oil level
monitor. Usually, the monitor has two contacts for alarm. One contact is for
maximum oil level alarm and the other contact is for minimum oil level alarm.
The top-oil thermometer has a liquid thermometer bulb in a pocket at the top
of the transformer. The thermometer measures the top-oil temperature of the
transformer. The top-oil thermometer can have one to four contacts, which
sequentially close at successively higher temperature.
The figure below shows the construction of a capillary-type top-oil
thermometer, where the bulb is situated in a “pocket” surrounded by oil on
nitrogen gas.The simplest form of pressure relief device is the widely
used frangible disk. The surge of oil caused by a heavy internal fault bursts
the disk and allows the oil to discharge rapidly. Relieving and limiting the
pressure rise prevent explosive rupture of the tank and consequent fire.Also, if
used, the separate tap changer oil enclosure can be fitted with a pressure relief
device. The pressure relief device can be fitted with contact unit(s) to provide
a signal for circuit breaker(s) tripping circuits. A drawback of the frangible
disk is that the oil remaining in the tank is left exposed to the atmosphere
after a rupture. This is avoided in a more effective device, the pressure relief
valve, which opens to allow the discharge of oil if the pressure exceeds the
pre-adjusted limit. If the abnormal pressure is relatively high, this spring-
controlled valve can operate within a few milliseconds and provide fast
tripping when suitable contacts are fitted. The valve closes automatically as
the internal pressure falls below a critical level.
3. Oil Level Monitor Device
Transformers with oil conservator(s) (expansion tank) often have an oil level
monitor. Usually, the monitor has two contacts for alarm. One contact is for
maximum oil level alarm and the other contact is for minimum oil level alarm.
The top-oil thermometer has a liquid thermometer bulb in a pocket at the top
of the transformer. The thermometer measures the top-oil temperature of the
transformer. The top-oil thermometer can have one to four contacts, which
sequentially close at successively higher temperature.
The figure below shows the construction of a capillary-type top-oil
thermometer, where the bulb is situated in a “pocket” surrounded by oil on
top of the transformer. The bulb is connected to the measuring bellow inside
the main unit via a capillary tube. The bellow moves the indicator through
mechanical linkages, resulting in the operation of the contacts at set
temperatures.
The top-oil temperature may be considerably lower than the winding
temperature, especially shortly after a sudden load increase. This means that
the top-oil thermometer is not an effective overheating protection.
However, where the policy towards transformers’ loss of life permits, tripping
on top-oil temperature may be satisfactory. This has the added advantage of
directly monitoring the oil temperature to ensure that it does not reach the
flash temperature.
4. Winding Thermometer
The winding thermometer, shown in the figure below, responds to both the
top-oil temperature and the heating effect of the load current.
the main unit via a capillary tube. The bellow moves the indicator through
mechanical linkages, resulting in the operation of the contacts at set
temperatures.
The top-oil temperature may be considerably lower than the winding
temperature, especially shortly after a sudden load increase. This means that
the top-oil thermometer is not an effective overheating protection.
However, where the policy towards transformers’ loss of life permits, tripping
on top-oil temperature may be satisfactory. This has the added advantage of
directly monitoring the oil temperature to ensure that it does not reach the
flash temperature.
4. Winding Thermometer
The winding thermometer, shown in the figure below, responds to both the
top-oil temperature and the heating effect of the load current.
The winding thermometer creates an image of the hottest part of the
winding. The top-oil temperature is measured with a similar method as
introduced earlier. The measurement is further expanded with a current signal
proportional to the loading current in the winding.
This current signal is taken from a current transformer located inside the
bushing of that particular winding. This current is lead to a resistor element in
the main unit. This resistor heats up, and as a result of the current flowing
through it, it will in its turn heat up the measurement bellow, resulting in an
increased indicator movement.
The temperature bias is proportional to the resistance of the electric
heating (resistor) element .The result of the heat run provides data to adjust
the resistance and thereby the temperature bias. The bias should correspond
to the difference between the hot-spot temperature and the top-oil temperature.
The time constant of the heating of the pocket should match the time constant
of the heating of the winding .The temperature sensor then measures a
temperature that is equal to the winding temperature if the bias is equal to the
winding. The top-oil temperature is measured with a similar method as
introduced earlier. The measurement is further expanded with a current signal
proportional to the loading current in the winding.
This current signal is taken from a current transformer located inside the
bushing of that particular winding. This current is lead to a resistor element in
the main unit. This resistor heats up, and as a result of the current flowing
through it, it will in its turn heat up the measurement bellow, resulting in an
increased indicator movement.
The temperature bias is proportional to the resistance of the electric
heating (resistor) element .The result of the heat run provides data to adjust
the resistance and thereby the temperature bias. The bias should correspond
to the difference between the hot-spot temperature and the top-oil temperature.
The time constant of the heating of the pocket should match the time constant
of the heating of the winding .The temperature sensor then measures a
temperature that is equal to the winding temperature if the bias is equal to the
temperature difference and the time constants are equal .With four contacts
fitted, the two lowest levels are commonly used to start fans or pumps for
forced cooling, the third level to initiate an alarm and the fourth step to trip
load breakers or de-energize the transformer or both .In case a power
transformer is fitted with top-oil thermometer and winding thermometer, the
latter one normally takes care of the forced cooling control.
COMPONENTS OF POWER TRANSFORMER
BASIC PARTS OF A TRANSFORMER
These are the basic components of a transformer.
1. Laminated core
2. Windings
3. Insulating materials
4. Transformer oil
5. Tap changer
6. Oil Conservator
7. Breather
8. Cooling tubes
9. Buchholz Relay
10. Explosion vent
fitted, the two lowest levels are commonly used to start fans or pumps for
forced cooling, the third level to initiate an alarm and the fourth step to trip
load breakers or de-energize the transformer or both .In case a power
transformer is fitted with top-oil thermometer and winding thermometer, the
latter one normally takes care of the forced cooling control.
COMPONENTS OF POWER TRANSFORMER
BASIC PARTS OF A TRANSFORMER
These are the basic components of a transformer.
1. Laminated core
2. Windings
3. Insulating materials
4. Transformer oil
5. Tap changer
6. Oil Conservator
7. Breather
8. Cooling tubes
9. Buchholz Relay
10. Explosion vent
.CORE
The core acts as support to the winding in the transformer. It also provides a low
reluctance path to the flow of magnetic flux. It is made of laminated soft iron
core in order to reduce eddy current loss and Hysteresis loss. The composition
of a transformer core depends on such as factors voltage, current, and
frequency. The diameter of the transformer core is directly proportional to
copper loss and is inversely proportional to iron loss. If the diameter of the core
is decreased, the weight of the steel in the core is reduced, which leads to less
core loss of the transformer and the copper loss increase. When the diameter of
the core is increased, the vise versa occurs.
The core acts as support to the winding in the transformer. It also provides a low
reluctance path to the flow of magnetic flux. It is made of laminated soft iron
core in order to reduce eddy current loss and Hysteresis loss. The composition
of a transformer core depends on such as factors voltage, current, and
frequency. The diameter of the transformer core is directly proportional to
copper loss and is inversely proportional to iron loss. If the diameter of the core
is decreased, the weight of the steel in the core is reduced, which leads to less
core loss of the transformer and the copper loss increase. When the diameter of
the core is increased, the vise versa occurs.
Why are windings made of copper?
Copper has high conductivity. This minimizes losses as well as the amount of
copper needed for the winding (volume & weight of winding).
Copper has high ductility. This means it is easy to bend conductors into tight
windings around the transformer's core, thus minimizing the amount of copper
needed as well as the overall volume of the winding.
Winding
Two sets of winding are made over the transformer core and are insulated from
each other. Winding consists of several turns of copper conductors bundled
together, and connected in series.
Winding can be classified in two different ways:
Based on the input and output supply
Based on the voltage range
Within the input/output supply classification, winding are further categorized:
Primary winding - These are the winding to which the input voltage is applied.
Secondary winding - These are the winding to which the output voltage is
applied.
Within the voltage range classification, winding are further categorized:
High voltage winding - It is made of copper conductor. The number of turns
made shall be the multiple of the number of turns in the low voltage winding.
The conductor used will be thinner than that of the low voltage winding.
Low voltage winding - It consists of fewer number of turns than the high
voltage winding. It is made of thick copper conductors. This is because the
current in the low voltage winding is higher than that of high voltage winding.
Input supply to the transformers can be applied from either low voltage (LV) or
high voltage (HV) winding based on the requirement.
INSULATING MATERIALS
Insulating paper and cardboard are used in transformers to isolate primary and
secondary winding from each other and from the transformer core.
Transformer oil is another insulating material. Transformer oil performs two
important functions: in addition to insulating function, it can also cool the core
and coil assembly. The transformer's core and winding must be completely
immersed in the oil. Normally, hydrocarbon mineral oils are used as transformer
oil. Oil contamination is a serious problem because contamination robs the oil
of its dielectric properties and renders it useless as an insulating medium.
Copper has high conductivity. This minimizes losses as well as the amount of
copper needed for the winding (volume & weight of winding).
Copper has high ductility. This means it is easy to bend conductors into tight
windings around the transformer's core, thus minimizing the amount of copper
needed as well as the overall volume of the winding.
Winding
Two sets of winding are made over the transformer core and are insulated from
each other. Winding consists of several turns of copper conductors bundled
together, and connected in series.
Winding can be classified in two different ways:
Based on the input and output supply
Based on the voltage range
Within the input/output supply classification, winding are further categorized:
Primary winding - These are the winding to which the input voltage is applied.
Secondary winding - These are the winding to which the output voltage is
applied.
Within the voltage range classification, winding are further categorized:
High voltage winding - It is made of copper conductor. The number of turns
made shall be the multiple of the number of turns in the low voltage winding.
The conductor used will be thinner than that of the low voltage winding.
Low voltage winding - It consists of fewer number of turns than the high
voltage winding. It is made of thick copper conductors. This is because the
current in the low voltage winding is higher than that of high voltage winding.
Input supply to the transformers can be applied from either low voltage (LV) or
high voltage (HV) winding based on the requirement.
INSULATING MATERIALS
Insulating paper and cardboard are used in transformers to isolate primary and
secondary winding from each other and from the transformer core.
Transformer oil is another insulating material. Transformer oil performs two
important functions: in addition to insulating function, it can also cool the core
and coil assembly. The transformer's core and winding must be completely
immersed in the oil. Normally, hydrocarbon mineral oils are used as transformer
oil. Oil contamination is a serious problem because contamination robs the oil
of its dielectric properties and renders it useless as an insulating medium.
PARTS OF THE TRANSFORMER
CONSERVATOR
The conservator conserves the transformer oil. It is an airtight, metallic,
cylindrical drum that is fitted above the transformer. The conservator tank is
vented to the atmosphere at the top, and the normal oil level is approximately in
the middle of the conservator to allow the oil to expand and contract as the
temperature varies. The conservator is connected to the main tank inside the
transformer, which is completely filled with transformer oil through a pipeline.
BREATHER
CONSERVATOR
The conservator conserves the transformer oil. It is an airtight, metallic,
cylindrical drum that is fitted above the transformer. The conservator tank is
vented to the atmosphere at the top, and the normal oil level is approximately in
the middle of the conservator to allow the oil to expand and contract as the
temperature varies. The conservator is connected to the main tank inside the
transformer, which is completely filled with transformer oil through a pipeline.
BREATHER
BREATHER
The breather controls the moisture level in the transformer. Moisture can arise
when temperature variations cause expansion and contraction of the insulating
oil, which then causes the pressure to change inside the conservator. Pressure
changes are balanced by a flow of atmospheric air in and out of the conservator,
which is how moisture can enter the system.
If the insulating oil encounters moisture, it can affect the paper insulation or
may even lead to internal faults. Therefore, it is necessary that the air entering
the tank is moisture-free.
The transformer's breather is a cylindrical container that is filled with silica gel.
When the atmospheric air passes through the silica gel of the breather, the air's
moisture is absorbed by the silica crystals. The breather acts like an air filter for
the transformer and controls the moisture level inside a transformer. It is
connected to the end of breather pipe.
TAP CHANGER
The output voltage of transformers vary according to
its input voltage and the load. During loaded
conditions, the voltage on the output terminal
decreases, whereas during off-load conditions the
output voltage increases. In order to balance the
voltage variations, tap changers are used. Tap changers can be either on-load tap
changers or off-load tap changers. In an on-load tap changer, the tapping can be
changed without isolating the transformer from the supply. In an off-load tap
changer, it is done after disconnecting the transformer. Automatic tap changers
are also available.
OFF LOAD TAPCHANGER (OLTC)
To change the turns ratio on the source winding, a switch is operated by a hand
wheel on the exterior of the tank. The handwheel is used to operate a switch
within the tank via an exterior operating rod and interior insulated operating
rods. The switch takes the form of fixed terminals or contacts arranged in a
circle. Turning the handwheel moves the contact or finger around the centre of
the circle to complete the circuit and give the desired ratio. This is known as
changing tap positions and is performed with the transformer off potential since
these switches cannot open a circuit carrying current.
The breather controls the moisture level in the transformer. Moisture can arise
when temperature variations cause expansion and contraction of the insulating
oil, which then causes the pressure to change inside the conservator. Pressure
changes are balanced by a flow of atmospheric air in and out of the conservator,
which is how moisture can enter the system.
If the insulating oil encounters moisture, it can affect the paper insulation or
may even lead to internal faults. Therefore, it is necessary that the air entering
the tank is moisture-free.
The transformer's breather is a cylindrical container that is filled with silica gel.
When the atmospheric air passes through the silica gel of the breather, the air's
moisture is absorbed by the silica crystals. The breather acts like an air filter for
the transformer and controls the moisture level inside a transformer. It is
connected to the end of breather pipe.
TAP CHANGER
The output voltage of transformers vary according to
its input voltage and the load. During loaded
conditions, the voltage on the output terminal
decreases, whereas during off-load conditions the
output voltage increases. In order to balance the
voltage variations, tap changers are used. Tap changers can be either on-load tap
changers or off-load tap changers. In an on-load tap changer, the tapping can be
changed without isolating the transformer from the supply. In an off-load tap
changer, it is done after disconnecting the transformer. Automatic tap changers
are also available.
OFF LOAD TAPCHANGER (OLTC)
To change the turns ratio on the source winding, a switch is operated by a hand
wheel on the exterior of the tank. The handwheel is used to operate a switch
within the tank via an exterior operating rod and interior insulated operating
rods. The switch takes the form of fixed terminals or contacts arranged in a
circle. Turning the handwheel moves the contact or finger around the centre of
the circle to complete the circuit and give the desired ratio. This is known as
changing tap positions and is performed with the transformer off potential since
these switches cannot open a circuit carrying current.
UNDERLOAD TAPCHANGER (ULTC)
To respond to changing voltage levels on the load side of the transformer is
accomplished by adjusting the transformers turns ratios. The underload
tapchanger switch is designed to change the tapped windings while carrying
load current. It is normally operated by a motor and can be operated by hand.
The tapchanger can be located electrically in the low voltage winding or
electrically in the neutral end of the high voltage winding. The motor and
control cabinet for the tapchanger is located on the side of the transformer
COOLING TUBES
Cooling tubes are used to cool the transformer oil. The transformer oil is
circulated through the cooling tubes. The circulation of the oil may either be
natural or forced. In natural circulation, when the temperature of the oil rises the
hot oil naturally rises to the top and the cold oil sinks downward. Thus the oil
naturally circulates through the tubes. In forced circulation, an external pump is
used to circulate the oil.
BUCHHOLZ RELAY
The Buchholz Relay is a protective device container housed over the connecting
pipe from the main tank to the conservator tank. It is used to sense the faults
occurring inside the transformer. It is a simple relay that is operated by the
gases emitted during the decomposition of transformer oil during internal faults.
It helps in sensing and protecting the transformer from internal faults.
EXPLOSION VENT
The explosion vent is used to expel boiling oil in the transformer during heavy
internal faults in order to avoid the explosion of the transformer. During heavy
faults, the oil rushes out of the vent. The level of the explosion vent is normally
maintained above the level of the conservatory tank.
SAFETY
Safety is of primary concern when working around a transformer. The
substation transformer is usually the highest voltage item in a facility’s
electrical distribution system. The higher voltages found at the transformer
deserve the respect and complete attention of anyone working in the area. A 6.6
kV system will arc to ground over 1.5 to 2.5 in. However, to extinguish that
same arc will require a separation of 15 in. Therefore, working around
energized conductors is not recommended for anyone but the qualified
To respond to changing voltage levels on the load side of the transformer is
accomplished by adjusting the transformers turns ratios. The underload
tapchanger switch is designed to change the tapped windings while carrying
load current. It is normally operated by a motor and can be operated by hand.
The tapchanger can be located electrically in the low voltage winding or
electrically in the neutral end of the high voltage winding. The motor and
control cabinet for the tapchanger is located on the side of the transformer
COOLING TUBES
Cooling tubes are used to cool the transformer oil. The transformer oil is
circulated through the cooling tubes. The circulation of the oil may either be
natural or forced. In natural circulation, when the temperature of the oil rises the
hot oil naturally rises to the top and the cold oil sinks downward. Thus the oil
naturally circulates through the tubes. In forced circulation, an external pump is
used to circulate the oil.
BUCHHOLZ RELAY
The Buchholz Relay is a protective device container housed over the connecting
pipe from the main tank to the conservator tank. It is used to sense the faults
occurring inside the transformer. It is a simple relay that is operated by the
gases emitted during the decomposition of transformer oil during internal faults.
It helps in sensing and protecting the transformer from internal faults.
EXPLOSION VENT
The explosion vent is used to expel boiling oil in the transformer during heavy
internal faults in order to avoid the explosion of the transformer. During heavy
faults, the oil rushes out of the vent. The level of the explosion vent is normally
maintained above the level of the conservatory tank.
SAFETY
Safety is of primary concern when working around a transformer. The
substation transformer is usually the highest voltage item in a facility’s
electrical distribution system. The higher voltages found at the transformer
deserve the respect and complete attention of anyone working in the area. A 6.6
kV system will arc to ground over 1.5 to 2.5 in. However, to extinguish that
same arc will require a separation of 15 in. Therefore, working around
energized conductors is not recommended for anyone but the qualified
professional. The best way to ensure safety when working around high voltage
apparatus is to make absolutely certain that it is de-energized.
Although inspections and sampling can usually be performed while the
transformer is in service, all other service and testing functions will require that
the transformer is de-energized and locked out. This means that a thorough
understanding of the transformer’s circuit and the disconnecting methods should
be reviewed before any work is performed.
A properly installed transformer will usually have a means for disconnecting
both the primary and the secondary sides; ensure that they are opened before
any work is performed. Both disconnects should be opened because it is
possible for generator or induced power to back feed into the secondary and
step up into the primary. After verifying that the circuit is de-energized at the
source, the area where the work is to be performed should be checked for
voltage with a “hot stick” or some other voltage indicating device.
It is also important to ensure that the circuit stays de-energized until the work is
completed. This is especially important when the work area is not in plain view
of the disconnect. Red or orange lock-out tags should be applied to all breakers
and disconnects that will be opened for a service procedure. The tags should be
highly visible, and as many people as possible should be made aware of their
presence before the work begins.
Some switches are equipped with physical locking devices (a hasp or latch).
This is the best method for locking out a switch. The person performing the
work should keep the key at all times, and tags should still be applied in case
other keys exist.
After verifying that all circuits are de-energized, grounds should be connected
between all items that could have a different potential. This means that all
conductors, hoses, ladders and other equipment should be grounded to the tank,
and that the tank’s connection to ground should be verified before beginning
any work on the transformer. Static charges can be created by many
maintenance activities, including cleaning and filtering. The transformer’s
inherent ability to step up voltages and currents can create lethal quantities of
electricity.
The inductive capabilities of the transformer should also be considered when
working on a de-energized unit that is close to other conductors or devices that
are energized. A de-energized transformer can be affected by these energized
items, and dangerous currents or voltages can be induced in the adjacent
windings.
apparatus is to make absolutely certain that it is de-energized.
Although inspections and sampling can usually be performed while the
transformer is in service, all other service and testing functions will require that
the transformer is de-energized and locked out. This means that a thorough
understanding of the transformer’s circuit and the disconnecting methods should
be reviewed before any work is performed.
A properly installed transformer will usually have a means for disconnecting
both the primary and the secondary sides; ensure that they are opened before
any work is performed. Both disconnects should be opened because it is
possible for generator or induced power to back feed into the secondary and
step up into the primary. After verifying that the circuit is de-energized at the
source, the area where the work is to be performed should be checked for
voltage with a “hot stick” or some other voltage indicating device.
It is also important to ensure that the circuit stays de-energized until the work is
completed. This is especially important when the work area is not in plain view
of the disconnect. Red or orange lock-out tags should be applied to all breakers
and disconnects that will be opened for a service procedure. The tags should be
highly visible, and as many people as possible should be made aware of their
presence before the work begins.
Some switches are equipped with physical locking devices (a hasp or latch).
This is the best method for locking out a switch. The person performing the
work should keep the key at all times, and tags should still be applied in case
other keys exist.
After verifying that all circuits are de-energized, grounds should be connected
between all items that could have a different potential. This means that all
conductors, hoses, ladders and other equipment should be grounded to the tank,
and that the tank’s connection to ground should be verified before beginning
any work on the transformer. Static charges can be created by many
maintenance activities, including cleaning and filtering. The transformer’s
inherent ability to step up voltages and currents can create lethal quantities of
electricity.
The inductive capabilities of the transformer should also be considered when
working on a de-energized unit that is close to other conductors or devices that
are energized. A de-energized transformer can be affected by these energized
items, and dangerous currents or voltages can be induced in the adjacent
windings.
Most electrical measurements require the application of a potential, and these
potentials can be stored, multiplied, and discharged at the wrong time if the
proper precautions are not taken. Care should be taken during the tests to ensure
that no one comes in contact with the transformer while it is being tested. Set up
safety barriers, or appoint safety personnel to secure remote test areas. After a
test is completed, grounds should be left on the tested item for twice the
duration of the test, preferably longer.
Once the operation of the transformer is understood, especially its inherent
ability to multiply voltages and currents, then safety practices can be applied
and modified for the type
TYPES OF TRANSFORMER INSTALLED IN PLANT
• Generator transformer
• Station transformers
• Excitation Transformer
• MV/LV Transformers
• Lighting Transformers
potentials can be stored, multiplied, and discharged at the wrong time if the
proper precautions are not taken. Care should be taken during the tests to ensure
that no one comes in contact with the transformer while it is being tested. Set up
safety barriers, or appoint safety personnel to secure remote test areas. After a
test is completed, grounds should be left on the tested item for twice the
duration of the test, preferably longer.
Once the operation of the transformer is understood, especially its inherent
ability to multiply voltages and currents, then safety practices can be applied
and modified for the type
TYPES OF TRANSFORMER INSTALLED IN PLANT
• Generator transformer
• Station transformers
• Excitation Transformer
• MV/LV Transformers
• Lighting Transformers
Figure 6: 140 MVA Generator transformer
SPECIFICATIONS OF THE TRANSFORMERS USED IN PLANT:-
GENERATOR TRANSFORMER
Three Phase, 50 Hz, 140 MVA, Fuji Electric Company.
This is a Step up Transformer.
Vector group - Delta Star11 (YNd11) , neutral solidly grounded.
Welded tank construction.
Type of cooling - Oil forced air forced cooling(OFAF).
CT (500/5 A) is used for Winding temp. Indicator.
NVTC (NO voltage Tape Changer) for voltage control (off load). It must
be operated only at no voltage.
Temp. Rise Windings 55
o
C
Oil 50
o
C
Max Ambient Temp = 50
o
C
HV LV
Rated Power (MVA)= 115 115
Rated Voltage (kV) = 290 11.5
Rate current(A) = 290 5774
% Impedance Voltage (HV –LV at 115 MVA) = 12.26 %
STATION TRANSFORMER
Three Phase, 24 MVA, Fuji Electric Company.
This is a Step down Transformer.
On load Tape Changer Device
.
Vector group - Delta Star11 (YNd11) , neutral solidly grounded.
SPECIFICATIONS OF THE TRANSFORMERS USED IN PLANT:-
GENERATOR TRANSFORMER
Three Phase, 50 Hz, 140 MVA, Fuji Electric Company.
This is a Step up Transformer.
Vector group - Delta Star11 (YNd11) , neutral solidly grounded.
Welded tank construction.
Type of cooling - Oil forced air forced cooling(OFAF).
CT (500/5 A) is used for Winding temp. Indicator.
NVTC (NO voltage Tape Changer) for voltage control (off load). It must
be operated only at no voltage.
Temp. Rise Windings 55
o
C
Oil 50
o
C
Max Ambient Temp = 50
o
C
HV LV
Rated Power (MVA)= 115 115
Rated Voltage (kV) = 290 11.5
Rate current(A) = 290 5774
% Impedance Voltage (HV –LV at 115 MVA) = 12.26 %
STATION TRANSFORMER
Three Phase, 24 MVA, Fuji Electric Company.
This is a Step down Transformer.
On load Tape Changer Device
.
Vector group - Delta Star11 (YNd11) , neutral solidly grounded.
Welded tank construction.
Type of cooling Oil natural air natural cooling.
OLTC for 6.6 kV Bus voltage control.
Tapping is done always secondary winding or High Voltage side . Because
Of two reasons:-
In HV side ,current is less.
There is higher turns in HV side , So fine tuning is
performed.
DIFFERENT TESTING OF TRANSFORMER
1. Transformer winding resistance measurement
2. Transformer ratio test.
3. Oil testing(B.D.V ,PPM(moisture) ,DGA )
4. Tan delta testing[Cap.(nominal)=capacitance(measured)]
5. Transformer vector group test.
6. Measurement of impedance voltage/short circuit impedance (principal tap)
and load loss (Short circuit test).
7. Measurement of no load loss and current (Open circuit test).
8. Measurement of insulation resistance(IR).
9. Dielectric tests of transformer.
10. Temperature rise test of transformer.
11. Tests on on-load tap-changer.
12. Vacuum tests on tank and radiators.
TRANSFORMER WINDING RESISTANCE MEASUREMENT
Transformer winding resistance measurement is carried out to calculate the I
2
R
losses and to calculate winding temperature at the end of a temperature rise test.
It is carried out as a type test as well as routine test. It is also done at site to
ensure healthiness of a transformer that is to check loose connections, broken
strands of conductor, high contact resistance in tap changers, high voltage leads
and bushings etc. There are different methods for measuring of transformer
winding, likewise
(1) Current-voltage method of measurement of winding resistance.
(2) Bridge method of measurement of winding resistance.
(3) Kelvin bridge method of Measuring Winding Resistance.
(4)Measuring winding resistance by Automatic Winding Resistance
Measurement Kit.
Type of cooling Oil natural air natural cooling.
OLTC for 6.6 kV Bus voltage control.
Tapping is done always secondary winding or High Voltage side . Because
Of two reasons:-
In HV side ,current is less.
There is higher turns in HV side , So fine tuning is
performed.
DIFFERENT TESTING OF TRANSFORMER
1. Transformer winding resistance measurement
2. Transformer ratio test.
3. Oil testing(B.D.V ,PPM(moisture) ,DGA )
4. Tan delta testing[Cap.(nominal)=capacitance(measured)]
5. Transformer vector group test.
6. Measurement of impedance voltage/short circuit impedance (principal tap)
and load loss (Short circuit test).
7. Measurement of no load loss and current (Open circuit test).
8. Measurement of insulation resistance(IR).
9. Dielectric tests of transformer.
10. Temperature rise test of transformer.
11. Tests on on-load tap-changer.
12. Vacuum tests on tank and radiators.
TRANSFORMER WINDING RESISTANCE MEASUREMENT
Transformer winding resistance measurement is carried out to calculate the I
2
R
losses and to calculate winding temperature at the end of a temperature rise test.
It is carried out as a type test as well as routine test. It is also done at site to
ensure healthiness of a transformer that is to check loose connections, broken
strands of conductor, high contact resistance in tap changers, high voltage leads
and bushings etc. There are different methods for measuring of transformer
winding, likewise
(1) Current-voltage method of measurement of winding resistance.
(2) Bridge method of measurement of winding resistance.
(3) Kelvin bridge method of Measuring Winding Resistance.
(4)Measuring winding resistance by Automatic Winding Resistance
Measurement Kit.
TRANSFORMER RATIO TEST
The performance of a transformer largely depends upon perfection of specific
turns or voltage ratio of transformer. So transformer ratio test is an essential
type test of transformer. This test also performed as routine test of transformer.
So for ensuring proper performance of electrical power transformer, voltage and
turn ratio test of transformer one of the vital tests. The procedure of transformer
ratio test is simple. We just apply three phase 415 V supply to HV winding,
with keeping LV winding open. The we measure the induced voltages at HV
and LV terminals of transformer to find out actual voltage ratio of transformer.
We repeat the test for all tap position separately
MAINTENANCE
Heat and contamination are the two greatest enemies to the transformer’s
operation. Heat will break down the solid insulation and accelerate the chemical
reactions that take place when the oil is contaminated. All transformers require
a cooling method and it is important to ensure that the transformer has proper
cooling. Proper cooling usually involves cleaning the cooling surfaces,
maximizing ventilation, and monitoring loads to ensure the transformer is not
producing excess heat.
Contamination is detrimental to the transformer, both inside and out. The
importance of basic cleanliness and general housekeeping becomes evident
when long term service life is considered. Dirt builds up and grease deposits
severely limit the cooling abilities of radiators and tank surfaces. Terminal and
insulation surfaces are especially susceptible to dirt and grease build up. Such
buildup will usually affect test results. The transformer’s general condition
should be noted during any activity, and every effort should be made to
maintain its integrity during all operations.
The oil in the transformer should be kept as pure as possible. Dirt and moisture
will start chemical reactions in the oil that lower both its electrical strength and
its cooling capability. Contamination should be the primary concern any time
the transformer must be opened. Most transformer oil is contaminated to some
degree before it leaves the refinery. It is important to determine how
contaminated the oil is and how fast it is degenerating. Determining the degree
of contamination is accomplished by sampling and analyzing the oil on a
regular basis.
The performance of a transformer largely depends upon perfection of specific
turns or voltage ratio of transformer. So transformer ratio test is an essential
type test of transformer. This test also performed as routine test of transformer.
So for ensuring proper performance of electrical power transformer, voltage and
turn ratio test of transformer one of the vital tests. The procedure of transformer
ratio test is simple. We just apply three phase 415 V supply to HV winding,
with keeping LV winding open. The we measure the induced voltages at HV
and LV terminals of transformer to find out actual voltage ratio of transformer.
We repeat the test for all tap position separately
MAINTENANCE
Heat and contamination are the two greatest enemies to the transformer’s
operation. Heat will break down the solid insulation and accelerate the chemical
reactions that take place when the oil is contaminated. All transformers require
a cooling method and it is important to ensure that the transformer has proper
cooling. Proper cooling usually involves cleaning the cooling surfaces,
maximizing ventilation, and monitoring loads to ensure the transformer is not
producing excess heat.
Contamination is detrimental to the transformer, both inside and out. The
importance of basic cleanliness and general housekeeping becomes evident
when long term service life is considered. Dirt builds up and grease deposits
severely limit the cooling abilities of radiators and tank surfaces. Terminal and
insulation surfaces are especially susceptible to dirt and grease build up. Such
buildup will usually affect test results. The transformer’s general condition
should be noted during any activity, and every effort should be made to
maintain its integrity during all operations.
The oil in the transformer should be kept as pure as possible. Dirt and moisture
will start chemical reactions in the oil that lower both its electrical strength and
its cooling capability. Contamination should be the primary concern any time
the transformer must be opened. Most transformer oil is contaminated to some
degree before it leaves the refinery. It is important to determine how
contaminated the oil is and how fast it is degenerating. Determining the degree
of contamination is accomplished by sampling and analyzing the oil on a
regular basis.
CONCLUSION:-
After analyzing the NTPC, Kawas Gas Power Plant
656.2 MW combined cycle power plant, I can describe
that this power plant is very efficient one as compare to
other power plant that runs based on open cycle. Also I
would like to add up that it is very compact in size, less
pollute in nature, easily controlled and decent power
plant that I had ever seen.
And from the study of renewable sources we can
conclude that there is a large scope in them and
government is also taking initiatives for the use of
renewable sources.
I really had a nice time here and got a treasure of
practical knowledge from the NTPC employees. In
future I am sure that this vocational training in NTPC is
going to help me in my rest of the studies.
Indeed ,The industrial training at NTPC , Kawas
has been a very good learning experience for me. The
knowledge of theoretical subject is not enough for any
engineering stream. One has to have the practical
knowledge to remove the gap between the actual and
expected performance.
After analyzing the NTPC, Kawas Gas Power Plant
656.2 MW combined cycle power plant, I can describe
that this power plant is very efficient one as compare to
other power plant that runs based on open cycle. Also I
would like to add up that it is very compact in size, less
pollute in nature, easily controlled and decent power
plant that I had ever seen.
And from the study of renewable sources we can
conclude that there is a large scope in them and
government is also taking initiatives for the use of
renewable sources.
I really had a nice time here and got a treasure of
practical knowledge from the NTPC employees. In
future I am sure that this vocational training in NTPC is
going to help me in my rest of the studies.
Indeed ,The industrial training at NTPC , Kawas
has been a very good learning experience for me. The
knowledge of theoretical subject is not enough for any
engineering stream. One has to have the practical
knowledge to remove the gap between the actual and
expected performance.
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