Report ntpc auraiya

1. ABSTRACT

to meet the power demands of the country, it is required to set up new project,
time to time so that demand and generation gap may be narrowed but most
important is to full utilization of existing capacity .this may be possible only by
increasing the reliability, availability, maintainability of power generation
units and by operating the units at its full capacity.
This vocational training report is concerned with the overall operation of the
plant, water treatment in the plant and thermodynamic cycles used in NTPC,
Auraiya gas power station.

2. AKNOWLEDGEMENT

A summer project is a golden opportunity for learning and self development . I
consider myself very lucky and honored to have a opportunity provided by
NTPC.

I wish to express my indebted gratitude and special thanks to " MR. M.K.
Sharma sir, MANAGER (HR-EDC) NTPC, auraiya" who in spite of being
extraordinarily busy with his duties, took time to manage the whole summer
training in proper way and allowing me to carry out my industrial training work
at their esteemed organization.

A humble ‘Thank you’ Sir.

It is my glowing feeling to place on record my best regards, deepest sense of
gratitude to all the engineers (associated in NTPC) for their judicious and
precious lectures and guidance about the operation of power plant. which were
extremely valuable for my study both theoretically and practically.

I express my deepest thanks to MR. S.K. Verma sir for their guidance and
support. He supported to us by showing different method of information
collection about the company. He helped all time when we needed and he gave
right direction toward completion of project.

At the last but not least my humble thanks to all who helped me in complearing
my summer training project.
(Gopesh kumar)

Place:- NTPC dibiyapur auraiya

Date:- 22th july 2014

3. -:CONTENTS:-
 INTRODUCTION TO NTPC
 TOTAL INSTALLED CAPACITY OF NTPC
 INTRODUCTION OF NTPC,AURAIYA GAS POWER STATION
 COMBINED CYCLE AND COMBINED CYCLE PLANT
 AIR COMPRESSOR AND COMBUSTION CHAMBER
 FULES
 TURBINES AND GAS TURBINE LAYOUT OF NTPC, AURAIYA
 BOILERS AND WASTE HEAT RECOVERY BOILERS
 BOILER ECONOMISER AND WASTE HEAT RECOVERY
 WATER TREATMENT PLANT,STORAGE AND RESORCES
 STEAM TURBINE
 VOLTAGE GENERATOR
 PASSOUT OR EXTRACTIO TURBINE
 CIRCULATING WATER PUMP AND DEAERATOR
 COOLING SYSTEM
 CONTROLE SYSTEM OF THE PLANT
 ELECTRICAL AND SWITCHYARD DEPARTMENT
 DEFFFERENT TYPE OF EQUIPMENT USED IN SUB STATIONS
 CONCLUSION
 REFFERENCE

4. INTRODUCTION:-


Figure :- image from main plant NTPC auraiya

NTPC Limited (formerly known as National Thermal Power Corporation
Limited) is a Central Public Sector Undertaking (CPSU) under the Ministry
of Power, Government of India. It is the largest power company in India
with an electric power generating capacity of 43,128 MW. Although the
company has approx. 18% of the total national capacity it contributes to
over 27% of total power generation due to its focus on operating its power
plants at higher efficiency levels (approx. 83% against the
national PLF rate of 78%)
It was founded by Government of India in 1975, which held 75% of its
equity shares on 31 March 2013 (after divestment of its stake in 2004,
2010 and 2013).
In May 2010, NTPC was conferred Maharatna status by the Union
Government of India. It is listed in Forbes Global 2000 for 2014 at 424th
rank in the world.

5. NTPC IN INDIAN POWER SECTOR:-

7. Presently, NTPC generates power from Coal and Gas. With an installed
capacity of 43,128 MW, NTPC is the lairgest power generating major in the
country. It has also diversified into hydro power, coal mining, power equipment
manufacturing, oil & gas exploration, power trading & distribution. With an
increasing presence in the power value chain, NTPC is well on its way to
becoming an “Integrated Power Major.”



INSTALLED CAPACITY:-
Present installed capacity of NTPC is 43,128 MW (including 5,974 MW through JVs)
comprising of 38 NTPC Stations (17 Coal based stations, 7 combined cycle gas/liquid
fuel based stations), 7 Joint Venture stations (6 coal based and one gas based) and 7
renewable energy projects.


NO. OF PLANTS CAPACITY (MW)
NTPC Owned
Coal 17 33,015
Gas/Liquid Fuel 7 4,044
Renewable energy projects 7 95
Total 31 37,154
Owned By JVs
Coal & Gas 7 5,974
Total 38 43,128

Regional Spread of Generating Facilities

REGION COAL GAS Renewable TOTAL
Northern 9,015 2,334 20 11,369
Western 10,840 1,313 50 12,203
Southern 4,600 370 15 4,975
Eastern 8,560 - 10 8,570
JVs 4,034 1,967 - 6,001
Total 37,049 5,984 95 43,128

8. PROJECT PROFILE:-

COAL BASED POWER STATIONS:-

With 17 coal based power stations, NTPC is the largest thermal power generating
company in the country. The company has a coal based installed capacity of 33,015 MW.



COAL BASED(Owned by
NTPC)
STATE
COMMISSIONED
CAPACITY(MW)
1. Singrauli Uttar Pradesh 2,000
2. Korba Chhattisgarh 2,600
3. Ramagundam Telangana 2,600
4. Farakka West Bengal 2,100
5. Vindhyachal Madhya Pradesh 4,260
6. Rihand Uttar Pradesh 3,000
7. Kahalgaon Bihar 2,340
8. Dadri Uttar Pradesh 1,820
9. Talcher Kaniha Orissa 3,000
10. Feroze Gandhi, Unchahar Uttar Pradesh 1,050
11. Talcher Thermal Orissa 460
12. Simhadri Andhra Pradesh 2,000
13. Tanda Uttar Pradesh 440
14. Badarpur Delhi 705
15. Sipat Chhattisgarh 2,980
16. Mauda Maharashta 1,000
17. Barh Bihar 660
Total 33,015

9. Coal Based Joint Ventures:


COAL BASED
(Owned by JVs)
STATE
COMMISSIONED
CAPACITY
1. Durgapur West Bengal 120
2. Rourkela Orissa 120
3. Bhilai Chhattisgarh 574
4. Kanti Bihar 220
5. IGSTPP, Jhajjar Haryana 1500
6. Vallur Tamil Nadu 1500
Total 4,034


GAS/LIQUID FUEL BASED POWER STATIONS:-

The details of NTPC gas based power stations is as follows


GAS BASED
(Owned by NTPC)
STATE
COMMISSIONED
CAPACITY(MW)
1. Anta Rajasthan 419.33
2. Auraiya Uttar Pradesh 663.36
3. Kawas Gujarat 656.20
4. Dadri Uttar Pradesh 829.78
5. Jhanor-Gandhar Gujarat 657.39
6. Rajiv Gandhi CCPP Kayamkulam Kerala 359.58
7. Faridabad Haryana 431.59
Total 4,017.23

GAS BASED JOINT VENTURES:-


COAL BASED
(Owned by JVs)
STATE
COMMISSIONED
CAPACITY
1. RGPPL Maharashtra 1967.08
Total 1,967.08

10. FUTURE PLANNING:-

India’s current capacity of 233,930MW, NTPC accounts for 18.14% with an installed
power generation capacity of 43,128MW. The utility plans to add 14,038MW during the
12th Plan period (2012-17) and has budgeted capital expenditure of Rs.1.5 trillion. It has
set up a target of becoming a 128,000MW power producer by the year 2032.

11. INTRODUCTION TO GAS POWER STATION
NTPC (AURAIYA):-

Figure :- image from main plant NTPC auraiya

NTPC Auraiya is located at Dibiyapur in Auraiya district in the Indian state
of Uttar Pradesh. The power plant is one of the gas based power plants
of NTPC. The plant has 4 gas turbine(GT) and 2 steam turbine (ST)with 4 waste
heat recovery boiler(WHRB).The gas for the power plant is sourced
from GAIL HBJ Pipeline - South Basin Gas field. Source of water for the power
plant is Auraiya - Etawah Canal. Plant is basically devided in to two module
and each module has 2GTand 1ST and 2WHRB and their capacities are as
follows

MODULE 1:-
Gas turbine capacity : 2×111.19 MW
Steam turbine capacity: 109.3 MW
Total module1 capacity : 331.68 MW

12. MODULE 2:-
Same as module 1
Total module2 capacity: 3331.68 MW

TOTAL PLANT CAPACITY: 663.36 MW

CAPACITY:-

Stage
Unit
Number
Installed Capacity
(MW)
Date of
Commissioning
GT / ST
1
st
1 111.19 1989 March GT
1
st
2 111.19 1989 July GT
1
st
3 111.19 1989 August GT
1
st
4 111.19 1989 September GT
1
st
5 109.3 1989 December ST
1
st
6 109.3 1990 June ST
Total Six 663.36

13. THE BASIC DIAGRAM OF ARRANGEMENT OF
UNITS IN AURAIYA GAS POWER PLANT:-







STATION CAPACITY
663.36MW




















111.19MW 111.19MW 111.19MW 111.19MW

COMBINED CYCLE:-

Combining two or more thermodynamic cycles results in improved overall
efficiency, reducing fuel costs. In stationary power plants, a widely used
combination is a gas turbine (operating by the Brayton cycle) burning natural
gas or synthesis gas from coal, whose hot exhaust powers a steam power
plant (operating by the Rankine cycle). This is called a Combined Cycle Gas
MODULE #1
2×111.19 +109.3 =
331.68MW
MODULE# 2
2×111.19 +109.3 =
331.68MW


ST# 1
109.3 MW
ST# 2
109.3 MW

WHRB #1

WHRB#2 WHRB#3 WHRB#4
GT#1
111.19m
wWW
GT#1

GT#3 GT#4

14. Turbine (CCGT) plant, and can achieve a thermal efficiency of around 60%, in
contrast to a single cycle steam power plant which is limited to efficiencies of
around 35-42%.


Figure :-combined cycle diagram
COMBINED CYCLE PLANTS:-

The Combined Cycle Power Plant or combined cycle gas turbine, a gas turbine
generator generates electricity and waste heat is used to make steam to generate
additional electricity via a steam turbine. The gas turbine is one of the most
efficient one for the conversion of gas fuels to mechanical power or electricity.
The use of distillate liquid fuels, usually diesel, is also common as alternate
fuels.
More recently, as simple cycle efficiencies have improved and as natural gas
prices have fallen, gas turbines have been more widely adopted for base load
power generation, especially in combined cycle mode, where waste heat is
recovered in waste heat boilers, and the steam used to produce additional
electricity.
This system is known as a Combined Cycle. The basic principle of the
Combined Cycle is simple: burning gas in a gas turbine (GT) produces not only
power – which can be converted to electric power by a coupled generator – but
also fairly hot exhaust gases.

15. Figure - Combined cycle power plant scheme

Routing these gases through a water-cooled heat exchanger produces steam,
which can be turned into electric power with a coupled steam turbine and
generator.

16. COMBINED CYCLE OPERATION AT NTPC
AURAIYA:-




AIR COMPRESSOR:-

in thermal power plant. Compressed air plays the vital role in every gas turbine
plant. Gas turbine is used in power plant to drive the generator, by which we
can produce electricity with other arrangements.
Usually rotary air compressor is used with a gas turbine. Mostly centrifugal
compressors or axial compressors are used.
There are 4 compressor in the plant.4 used in GT and is used in emergency GT.
These are 19 stages series compressor.

Compressor pressor ratio is :- 6.9:1

17. COMBUSTION CHAMBER:-


Figure:- combustion chamber of gas turbine


The combustion process increases the internal energy of a gas, which translates
into an increase in temperature, pressure, or volume This increase in pressure or
volume can be used to do work

18. FUELS:-

Mainly two fuel are used in this gas power plant which are listed below

Natural gas
Neptha

Natural gas is supplied by GAIL, dibiyapur and taken directly from the
pipeline which goes from hazira to jagdishpur.
The other fuel is supplied by IOC ,Kanpur and Mathura













STORAGE CAPACITY FOR NEPTHA:-

There are two tanks for storarig neptha fuel each having a capacity of 1500KL.
There are three transfer pumps for loading fuel from tankers .the two pumps
works and third is auxiliary. There twelve unloading pipes ,thus twelve truck is
unloading at a time.
If turbine is running at full load then it consumes 20 KL neptha fuel in one
hour




Figure:-GAIL PATA Figure:-IOCL MATHURA

19. GAS TURBINE:-

A gas turbine, also called a combustion turbine, is a type of internal combustion
engine. It has an upstream rotating compressor coupled to a
downstream turbine, and a combustion chamber in-between.


Figure :-gas turbine

The basic operation of the gas turbine is similar to that of the steam power
plant except that air is used instead of water. Fresh atmospheric air flows
through a compressor that brings it to higher pressure. Energy is then added by
spraying fuel into the air and igniting it so the combustion generates a high-
temperature flow. This high-temperature high-pressure gas enters a turbine,
where it expands down to the exhaust pressure, producing a shaft work output in
the process. The turbine shaft work is used to drive the compressor and other
devices such as an electric generator that may be coupled to the shaft. The
energy that is not used for shaft work comes out in the exhaust gases, so these
have either a high temperature or a high velocity. The purpose of the gas turbine
determines the design so that the most desirable energy form is maximized. Gas
turbines are used to poweraircraft, trains, ships, electrical generators, or
even tanks.

20. GAS TURBINE LAYOUT OF NTPC ,AURAIYA:-


Gas turbine engines derive their power from burning fuel in a combustion
chamber and using the fast flowing combustion gases to drive a turbine in much
the same way as the high pressure steam drives a steam turbine.

One major difference however is that the gas turbine has a second turbine acting
as an air compressor mounted on the same shaft. The air turbine (compressor)
draws in air, compresses it and feeds it at high pressure into the combustion
chamber increasing the intensity of the burning flame.
It is a positive feedback mechanism. As the gas turbine speeds up, it also causes
the compressor to speed up forcing more air through the combustion chamber
which in turn increases the burn rate of the fuel sending more high pressure hot
gases into the gas turbine increasing its speed even more.
Uncontrolled runaway is prevented by controls on the fuel supply line which
limit the amount of fuel fed to the turbine thus limiting its speed.

The thermodynamic process used by the gas turbine is known as the Brayton
cycle. Analogous to the Carnot cycle in which the efficiency is maximised by
increasing the temperature difference of the working fluid between the input

21. and output of the machine, the Brayton cycle efficiency is maximised by
increasing the pressure difference across the machine. The gas turbine is
comprised of three main components: a compressor, a combustor, and a turbine.
The working fluid, air, is compressed in the compressor (adiabatic compression
- no heat gain or loss), then mixed with fuel and burned by the combustor under
constant pressure conditions in the combustion chamber (constant pressure heat
addition). The resulting hot gas expands through the turbine to perform work
(adiabatic expansion). Much of the power produced in the turbine is used to run
the compressor and the rest is available to run auxiliary equipment and do
useful work. The system is an open system because the air is not reused so that
the fourth step in the cycle, cooling the working fluid, is omitted.


Figure :-gas turbine


Gas turbines have a very high power to weight ratio and are lighter and smaller
than internal combustion engines of the same power. Though they are
mechanically simpler than reciprocating engines, their characteristics of high
speed and high temperature operation require high precision components and
exotic materials making them more expensive to manufacture.

22. ELECTRICAL POWER GENERATION:-

In electricity generating applications the turbine is used to drive a synchronous
generator which provides the electrical power output but because the turbine
normally operates at very high rotational speeds of 12,000 r.p.m or more it must
be connected to the generator through a high ratio reduction gear since the
generators run at speeds of 1,000 or 1,200 r.p.m. depending on the AC
frequency of the electricity grid.

TURBINE CONFIGURATIONS:-

Gas turbine power generators are used in two basic configurations
Simple Systems consisting of the gas turbine driving an electrical power
generator.



Combined Cycle Systems which are designed for maximum efficiency in which
the hot exhaust gases from the gas turbine are used to raise steam to power a
steam turbine with both turbines being connected to electricity generators.


Turbine Performance
Turbine Power Output

23. To minimise the size and weight of the turbine for a given output power, the
output per pound of airflow should be maximised. This is obtained by
maximising the air flow through the turbine which in turn depends on
maximising the pressure ratio between the air inlet and exhaust outlet. The main
factor governing this is the pressure ratio across the compressor which can be as
high as 40:1 in modern gas turbines. In simple cycle applications, pressure ratio
increases translate into efficiency gains at a given firing temperature, but there
is a limit since increasing the pressure ratio means that more energy will be
consumed by the compressor.

SYSTEM EFFICIENCY:-

Thermal efficiency is important because it directly affects the fuel consumption
and operating costs.


SIMPLE CYCLE TURBINES:-

A gas turbine consumes considerable amounts of power just to drive its
compressor. As with all cyclic heat engines, a higher maximum working
temperature in the machine means greater efficiency (Carnot's Law), but in a
turbine it also means that more energy is lost as waste heat through the hot
exhaust gases whose temperatures are typically well over 1,000°C .
Consequently simple cycle turbine efficiencies are quite low. For heavy plant,
design efficiencies range between 30% and 40%. (The efficiencies of aero
engines are in the range 38% and 42% while low power microturbines
(<100kW) achieve only 18% to 22%). Although increasing the firing
temperature increases the output power at a given pressure ratio, there is also a
sacrifice of efficiency due to the increase in losses due to the cooling air
required to maintain the turbine components at reasonable working
temperatures.

24. COMBINED CYCLE TURBINES:-

It is however possible to recover energy from the waste heat of simple cycle
systems by using the exhaust gases in a hybrid system to raise steam to drive a
steam turbine electricity generating set . In such cases the exhaust temperature
may be reduced to as low as 140°C enabling efficiencies of up to 60% to be
achieved in combined cycle systems.
In combined-cycle applications, pressure ratio increases have a less pronounced
effect on the efficiency since most of the improvement comes from increases in
the Carnot thermal efficiency resulting from increases in the firing temperature.

Thus simple cycle efficiency is achieved with high pressure ratios. Combined
cycle efficiency is obtained with more modest pressure ratios and greater firing
temperatures.


APPLICATIONS:-

Gas turbines can be used for large scale power generation. Examples are
applications delivering 600 MW or more from a 400 MW gas turbine coupled to
a 200 MW steam turbine in a co-generating installation. Such installations are
not normally used for base load electricity generation, but for bringing power to
remote sites such as oil and gas fields. They do however find use in the major
electricity grids in peak shaving applications to provide emergency peak power.
Low power gas turbine generating sets with capacities up to 5 MW can be
accommodated in transportation containers to provide mobile emergency
electricity supplies which can delivered by truck to the point of need.

25. BOILER:-
A boiler or steam generator is a device used to create steam by
applying heat energy to water. Although the definitions are somewhat
flexible, it can be said that older steam generators were commonly
termed boilers and worked at low to medium pressure (1–300 psi or
6.895–2,068.427 kPa) but, at pressures above this, it is more usual to speak
of a steam generator.
NTPC auraiya gas power plant has 4 waste haet recovery boiler . all the 4
boiler are non fired and water tube boiler

WASTE HEAT RECOVERY BOILERS (WHRB):-

a WHRB consist of a super heater ,a boiler ,an cconomizer and a stem drum .
waste heat recovery boiler may be horizontal or vertical shell boiler or water
tube boiler. they could be desined to suit indivisual application ranging through
gases from furnaces ,incinerators, gas turbine and die sel exhaust. the prim
requirment is that waste gasse must contain sufficient usable heat to produce
steam or hot water at the condition required.

26. Figure :-boiler configuration
some boilers may be dealt with my maintaining gas –exit at a pre determined
level to prevent dew point being reached and others by soot blowing. currently,
there is a string interest in small combined heat and power (CHP) stations,
thease will normally incorporate a wsta heat boiler.
WATER TREATMENT PLANT, STORAGE AND
RESORCE:-

Since steam is taken out continuously and returned to the boiler, losses due to
blow downs leakage have to have to be made up for mentaining designed boiler
water quantity by means of the level gauges provided on the boiler drum. For
this continuous make up water is added the boiler water system. Since this make
up requires pure water this quality water is obtained by demineralised
(DM) water treatment plant. For this purpose a storage tank installed from
which continuously DM water is drawn for boiler make up.

27. Figure :- figure shows the source and path followed by water


The impurities in water input to this plant generally consist calcium and
magnesium salts imparting hardness to the water . these salts have to be
removed from the water. If hardness present in make up water to the boiler, the
salt only from form deposits on the tube surface but also lead to overheating in
tose localities resulting in tube failures. Therefore these have to be compleatly
removed for use as boiler make up., this is done using DMwater treatment plant
which gives us purest form of water.

28. Figure :-water treatment plant


This is generally consist of CATION,ANION and mixed bed exchangers . the
final water from this process consist generally of hydrogen ion and hydroxide
ions which is the chemical composition of pure water . the DM water being very
pure is highly corrosive , once it absorbs oxygen from the atmosphere because
of its very high affinity for oxygen absorption. The capacity of DM plant is
dictated by the type and quantity of salt in the raw water input.
The storage tank for DM water is made from material not affected by corrosive
water such as PVC . The piping and valves are generally of stainless steel.

STEAM TURBINE:-

A steam turbine is a device that extracts thermal energy from
pressurized steam and uses it to do mechanical work on a rotating output shaft.
Its modern manifestation was invented by Sir Charles Parsons in 1884.
Because the turbine generates rotary motion, it is particularly suited to be used
to drive an electrical generator

29. Figure :-steam turbine

The first device that may be classified as a reaction steam turbine was little
more than a toy, the classic Aerolipile, described in the 1st century
by Greek mathematician Hero of Alexandria in Roman Egypt. In 1551, Taqi al-
Din in Ottoman Egypt described a steam turbine with the practical application
of rotating a spit. Steam turbines were also described by the Italian Giovanni
Branca (1629) and John Wilkins in England (1648).The devices described by
Taqi al-Din and Wilkins are today known as steam jacks.
The modern steam turbine was invented in 1884 by Sir Charles Parsons, whose
first model was connected to a dynamo that generated 7.5 kW (10 hp) of
electricity. The invention of Parsons' steam turbine made cheap and plentiful
electricity possible and revolutionized marine transport and naval warfare.

recently steam turbine have gained use in power plants and there are a large
number of neuclear plants that generate output in excess of 1000 megawatts by
powering massive steam turbine with high temperature steam generated by a
neuclear reactor .

30. in order to increase the efficiency of stem turbine , takasago machinery
works,mistubisi heavy industries limeted using 3D design technology to shape
rotor blades , developing and manufacturing larger rotor blades and designing
methods to prevent the loss of steam throughouts .

PASS OUT EXTRACTION TURBINE:-

the steam turbine used in NTPC , AURAIYA are pass out or extraction
turbines . in these types of turbine steam is exhausted at defferent stages and
used in heating the steam water for the boiler processing work .
the high pressure steam from boiler enters HP stage of turbine where it expands
and the pressure is reduced to such a value that is required for processing work
. a part of this low pressure steam leaving the high pressure stage is supplied to
the processing work while the remaining steam expand further in the L.P. stage.
The exhaust steam from the processing plant the low pressure turbine steam is
condensed in the condenser and pumped back to boiler.

31. GENERATOR HIGH-VOLTAGE SYSTEM:-

The generator voltage for modern utility-connected generators ranges from 11
kV in smaller units to 22 kV in larger units. The generator high-voltage leads
are normally large aluminium channels because of their high current as
compared to the cables used in smaller machines. They are enclosed in well-
grounded aluminium bus ducts and are supported on suitable insulators. The
generator high-voltage leads are connected to step-up transformers for
connecting to a high-voltage electrical substation (usually in the range of 115
kV to 765 kV) for further transmission by the local power grid.
The necessary protection and metering devices are included for the high-
voltage leads. Thus, the steam turbine generator and the transformer form one
unit. Smaller units may share a common generator step-up transformer with
individual circuit breakers to connect the generators to a common bus.
Phase - 3-Ф
Cooling - Hydrogen cooled
Speed - 3000 rpm
Frequency - 50 Hz
Excitation - DC Static excitation
Rated output - 111.19 MW (GTG) & 109.3 MW (STG)

32. Figure :- generator


CERCULATING WATER PUMP:-

These pumps are used to pump water to the deaerator from where the water
goes to boiler feed Pump.

DEAEREATOR:-

The deaerator are used to deaereator the water before feeding it in to BFP. This
is done because HRB is a water tube boiler and tubes containing water have
very small diameter . there are some gasses like CO2 if present in water they
can create rusting or can choke the tube . so these gasses are removed in the
deareator . there are total 4 deaereator in the NTPC , auraiya each for every
WHRB.

WORKING OF WHRB:-

The feed water enters in to steam drum through boiler economizer from where it
goes in to boiler and converted in to steam. This steam further goes to super

33. heater and at the output superheated stem at the temperature of 530C is ganed .
this superheated steam is used to drive steam turbine to generated electricity as
in the cycle.

COOLING SYSTEM:-

Why is Cooling Necessary?

power plants boils water to create steam, which then spins turbines to generate
electricity. The heat used to boil water can come from burning of a fuel, from
nuclear reactions, or directly from the sun or geothermal heat sources
underground. Once steam has passed through a turbine, it must be cooled back
into water before it can be reused to produce more electricity. Colder water
cools the steam more effectively and allows more efficient electricity
generation .

TYPES OF COOLING:-

Even though all thermoelectric plants use water to generate steam for electricity
generation, not all plant cooling systems use water. There are three main
methods of cooling:
Once-through systems take water from nearby sources (e.g., rivers, lakes,
aquifers, or the ocean), circulate it through pipes to absorb heat from the steam
in systems called condensers, and discharge the now warmer water to the local
source. Once-through systems were initially the most popular because of their
simplicity, low cost, and the possibility of siting power plants in places with
abundant supplies of cooling water. This type of system is currently widespread
in the eastern U.S. Very few new power plants use once-through cooling,
however, because of the disruptions such systems cause to local ecosystems
from the significant water withdrawals involved and because of the increased
difficulty in siting power plants near available water sources.

34. Figure:-wet cooling system

WET-RECIRCULATING OR CLOSED-LOOP:-

Power plants built after the 1960s shifted toward cooling systems that reuse
water, known as recirculating systems. systems reuse cooling water in a
second cycle rather than immediately discharging it back to the original water
source. At a recirculating system, water is kept in closed-loop piping so it can
be used repeatedly. Recirculating systems can consist of a cooling tower or a
cooling pond with both using ambient air to draw energy out of the cooling
water that was used to condense the steam. Most commonly, wet-recirculating
systems use cooling towers to expose water to ambient air. Some of the water
evaporates; the rest is then sent back to the condenser in the power plant.
Because wet-recirculating systems only withdraw water to replace any water
that is lost through evaporation in the cooling tower, these systems have much
lower water withdrawals than once-through systems, but tend to have
appreciably higher water consumption.

35. CONTROLE SYSTEM OF THE PLANT:-

There are three of controlling system available in the plant and they are as
follows :-


LOCAL CONTROLE:-

In this control commands are given to the machine from the place where
machine is located . this system is rarely used .

SWITCHYARD CONTROL :-

In it all controlling commands are given from switch gear room.

REMOTE SYSTEM:-

This system is frequently used . in it all controlling are given from central
computerised controle room ,there are two set of controlling devices . if one set
is shut down for maintenance then commands are given by second set.

ELECTRICAL AND SWITCHYARD DEPARTMENT:-

Electrical energy management system ensures at upply of energy to every
consumer at all times at rated voltage. Frequency and secified waveform at
lowest cost at minimum envoironmental degradation . the switch gear,
protection and network automation are integral part of modern energy
management system and national economy . the modern 3-ph ,50HZ,AC
interconnected system has several conventional and non conventional power
plants , GV transmission network ,substations ,MV and LV distribution system
and connected electrical load. the energy form is supplied to various consumers
located in vast geographical area instantly, automatically and safely with
required quality at all times. the service continuity and high quality of power
supply have become very important .

36. Figure :-switchyard

for fulfilment the foresaid purpose a state of the art scientifically and
technologically advanced substations is required .substations is the load control
center of the thermal plant where power at the rated voltage ,frequency and
waveform is exported , imported as per requirement
the substation at NTPC ,auraiya has two switch yard one of 220KV and other is
440KV . there are two bus bars and one transfer bus for supplying electricity .
after step up ,the 220KV output from the generator transfer is fed to either of
two bus bars through relays and circuit breakers and these are connected two
various feeders through various equipments.

There are 10 lines going out of NTPC, auraiya for supplying electricity. Their
descriptions are as follows :-

2 lines of 220KV to Agra.
2 lines of 440KV to Agra .
2 lines of 220KV to Maingaon , M.P.
2 lines of 220KV to GAIL , Dibiyapur.

37. DEFFERENT TYPE OF EQUIPMENTS USED IN SUB-
STATIONS:-

BUS BARS:-

Figurer:- bus bars

When a number of lines operating at the same voltage have to be directly
connected electrically, bus-bars are used as the common electrical component.
Bus-bars are copper or aluminium bars (generally of rectangular x-section) and
operate at constant voltage. The incoming and outgoing lines in a sub-station
are connected to the bus-bars. The most commonly used bus-bar arrangements
in sub-stations are :


Single bus-bar arrangement
Single bus-bar system with sectionalisation
Double bus-bar arrangement

INSULATOR:-

The insulators serve two purposes. They support the conductors (or bus-bars)
and confine the current to the conductors. The most commonly used material for
the manufacture of insulators is porcelain. There are several types of insulators

38. (e.g. pin type, suspension type, post insulator etc.) and their use in the sub-
station will depend upon the service requirement. For example, post insulator is
used for bus-bars. A post insulator consists of a porcelain body, cast iron cap
and flanged cast iron base. The hole in the cap is threaded so that bus-bars can
be directly bolted to the cap.

Isolating switches:-


Figure :- Isolators in typical sub station

In sub-stations, it is often desired to disconnect a part of the system for general
maintenance and repairs. This is accomplished by an isolating switch or
isolator. An isolator is essentially a knife switch and is designed to open a
circuit under no load. In other words, isolator switches are operated only when
the lines in which they are connected carry no current.
The entire sub-station has been divided into V sections. Each section can be
disconnected with the help of isolators for repair and maintenance.

39. CIRCUIT BREAKER:-


High voltage circuit breaker

A circuit breaker is an equipment which can open or close a circuit under
normal as well as fault conditions. It is so designed that it can be operated
manually (or by remote control) under normal conditions and automatically
under fault conditions. For the latter operation, a relay circuit is used with a
circuit breaker. Generally, bulk oil circuit breakers are used for voltages upto
66kV while for high (>66 kV) voltages, low oil circuit breakers are used. For
still higher voltages, air-blast, vacuum or SF6 circuit breakers are used.


LIGHTNING ARRESTERS:-


A lightning arrester is a device used
on electrical power systems
and telecommunications systems to protect
the insulation and conductors of the system
from the damaging effects of lightning. The

40. typical lightning arrester has a high-voltage terminal and a ground terminal.
When a lightning surge (or switching surge, which is very similar) travels along
the power line to the arrester, the current from the surge is diverted through the
arrestor, in most cases to earth.


POWER TRANSFORMER:-

A power transformer is used in a sub-station to step-up or step-down the
voltage. Except at the power station, all the subsequent sub-stations use step-
down transformers to gradually reduce the voltage of electric supply and finally
deliver it at utilisation voltage. The modern practice is to use 3-phase
transformers in sub-stations ; although 3 single phase bank of transformers can
also be used. The use of 3-phase transformer (instead of 3 single phase bank of
transformers) permits two advantages. Firstly, only one 3-phase load-tap
changing mechanism can be used. Secondly, its installation is much simpler
than the three single phase transformers. For ratings upto 10 MVA, naturally
cooled, oil immersed transformers are used. For higher ratings, the transformers
are generally air blast cooled.
Instrument Transformer
The lines in sub-stations operate at high voltages and carry current of thousands
of amperes. The measuring instruments and protective devices are designed for
low voltages (generally 110 V) and currents (about 5 A). Therefore, they will
not work satisfactorily if mounted directly on the power lines.


Figure :- transformers

41. This difficulty is overcome by installing instrument transformers on the power
lines. The function of these instrument transformers is to transfer voltages or
currents in the power lines to values which are convenient for the operation of
measuring instruments and relays. There are two types of instrument
transformers viz.


Current transformer (C.T.)
Potential transformer (P.T.)

CURRENT TRANSFORMER (C.T.):-

A current transformer is essentially a step-up transformer which steps down the
current to a known ratio. The primary of this transformer consists of one or
more turns of thick wire connected in series with the line. The secondary
consists of a large number of turns of fine wire and provides for the measuring
instruments and relays a current which is a constant fraction of the current in the
line. Suppose a current transformer rated at 100/5 A is connected in the line to
measure current. If the current in the line is 100 A, then current in the secondary
will be 5A. Similarly, if current in the line is 50A, then secondary of C.T. will
have a current of 2·5 A. Thus the C.T. under consideration will step down the
line current by a factor of 20.


VOLTAGE TRANSFORMER:-

It is essentially a step down transformer and steps down the voltage to a known
ratio. The primary of this transformer consists of a large number of turns of fine
wire connected across the line. The secondary winding consists of a few turns
and provides for measuring instruments and relays a voltage which is a known
fraction of the line voltage. Suppose a potential transformer rated at 66kV/110V
is connected to a power line. If line voltage is 66kV, then voltage across the
secondary will be 110 V.

42. METERING AND INDICATING INSTRUMENTS:-

There are several metering and indicating instruments (e.g. ammeters,
voltmeters, energy meters etc.) installed in a sub-station to maintain watch over
the circuit quantities. The instrument transformers are invariably used with them
for satisfactory operation.


MISCELLANEOUS EQUIPMENT:-

In addition to above, there may be following equipment in a sub-station :
fuses
carrier-current equipment
sub-station auxiliary supplies


RELAYS:-
In electrical engineering, a protective relay is a device designed to trip a circuit
breaker when a fault is detected. The first protective relays were
electromagnetic devices, relying on coils operating on moving parts to provide
detection of abnormal operating conditions such as over-current, over-voltage,
reverse power flow, over- and under- frequency.


Figure:-Protective relay

43. CONCLUSION:-

This is the vocational training report deals with over all operation of NTPC
plant in auraiya . also the report has a view of some paert used in plants.
The depleating resources of oil ,gas and coal (the conventional fuels) along with
atmosphere pollution problems have drawn the attentions of the scientists and
engineers all over the world to find out other sources for the generation of
electric power. There sources of energy are going to attain the nerve centre of
the future power plants. Though atomic and nuclear power plants have been
developed on conventional lines, but lot of work yet to be done. Efforts are
being made to atomic and nuclear energy directly into electric power with the
help of magneto hydrodynamic generator and other equipments.

REFFERENCES:-

 NTPC, Auraiya
 INTERNET