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1. DESIGN & OPTIMIZATION
OF 800 KV TRANSMISSION
LINE


Gopal Ji
AGM (Engineering TL Dept.)
Power Grid Corporation of India limited
Gurgaon, India

2. MAJOR COMPONENTS OF A
TRANSMISSION LINE
Conductor
Towers (and Foundations)
Earthwire
Insulators ] Insulator
Hardware Fittings ] strings
Accessories

3. BASIC DESIGN ASPECTS
Electrical Design Aspects
- Power Flow / Line Loadability
- Electrical Clearances (Operational, safety)
- Corona & Interference
- Insulation Requirements

Mechanical Design Aspects
- External (Dynamic) loads due to wind, ice etc.
- Self Weight of components
- Temperature conditions, Climatological factors
- Vibrations

TRANSMISSION LINE OPTMIZATION

Involves simultaneous/parallel studies for design &
selection of various components of transmission line
to achieve overall optimum techno-economic design

4. Review of
Existing systems
& Practices
Bundle Conductor
studies
Selection of
clearances
Insulator
string design
Tower Config.
Analysis
Tower Design
Study
Tower Fdn.
Study
Line Cost &
Optimization
Economic
Eval. Of Line
Results
TRANSMISSION LINE DESIGN OPTIMIZATION

5. DESIGN AND OPTIMISATION OF POWER
TRANSMISSION LINES

Review of existing system and practices
Selection of clearances
Insulator and insulator string design
Insulator
Hardware
Bundle conductor studies
Tower configuration analysis
Tower weight estimation
Foundation volumes estimation
Line cost analysis & span optimization
Economic evaluation of line

6. REVIEW OF EXISTING SYSTEM AND
PRACTICES

Review of practice adopted in different countries as
well as India w.r.t following

- Clearances adopted for different insulation levels
- Swing angles adopted and clearances thereof
- Configuration & Rating of insulator string, no of
discs per string
- Bundle conductor configuration, diameter of
conductor
- Surface gradient, Electric field, AN,TVI, RIV
limitations

7. SELECTION OF CLEARANCES

Tower Clearance (Strike Distance) for different swing
angles
Phase to Phase Spacing
Ground Clearance
Mid Span Clearance and Shielding Angle
Right of Way Clearance

8. SELECTION OF CLEARANCES

Strike distance (Live metal clearances): Clearance
requirements are to be based on two assumptions;
- In still air or under moderate winds, the clearance should be
sufficient to withstand the lightning or switching impulse voltages.
- Under high wind, the clearance should be adequate to meet the
power frequency voltage requirements.
Required Clearances are ascertained thru’ Insulation
Co-ordination Studies

Phase to Phase Clearances: Dictated by live metal clearances
for standard tower configurations adopted in India

Ground Clearances: Min clearance Based on I.E rules and
interference criteria (Electric field, surface gradient, AN, RIV)

Mid Span Clearance: Between earthwire and conductor: Based
on voltage level, span etc.

Right of Way Clearance: Based on I.E. rules

9. 16.0 M
Phase to
Phase
Clearance
765kV S/C TRANSMISSION LINE: RIGHT OF
WAY CALCULATIONS
9.0M + 17.5M +16.0 =42.5M ROW = 42.5 X 2 = 85M

7 m

MAXM.
SAG=14.5 M

21.5 sin 55 = 17.50 M
9.0 M elect.
Clearance required
as per IE Rules
MIN. GROUND CLEARANCE=15M

55 deg
swing
Insulator
string
Maximum sag of conductor

10. INSULATION CO-ORDINATION

Insulation co-ordination aims at selecting proper insulation
level for various voltage stresses in a rational manner. The
objective is to assure that insulation has enough strength to
meet the stress on it.



Over Voltage Probability Density

Insulation Flashover Probability

Voltage-kV
Stress
Strength
How many
Flashovers?

11. INSULATION CO-ORDINATION

The maximum over voltage occurs rarely and like wise insulation
strength very rarely decreases to its lowest value.

The likelihood of both events occurring simultaneously is very limited.

Therefore considerable economy may be achieved by recognizing the
probabilistic nature of both voltage stress and insulation strength and by
accepting a certain risk of failure.

This leads to substantial decrease in line insulation, spark distances,
tower dimensions, weight, ROW resulting in decreased cost of line.

The decrease in line cost must be weighed against the increased risk of
failure and the cost of such failures.

12. TYPICAL POWER FREQUENCY AC FLASHOVER
CHARACTERISTICS OF LARGE AIR GAPS
0
500
1000
1500
2000
2500
1 2 3 4 5 6
Gap Spacing,m
Critical Flashover Voltage
(Crest),kV
Rod to Plane
Insulator string
Conductor to Tower Leg
Conductor to Conductor
Vertical Rod to Rod TYPICAL AIR GAP SWITCHING SURGE CFO's
0
500
1000
1500
2000
2500
3000
34681012
Gap Spacing,m
Critical Flashover Voltage,kV
Rod to Plane
Tower Window
Horizontal Rod to Rod

13. BUNDLE CONDUCTOR SELECTION AND
OPTIMISATION
Size, Type and Configuration of Conductor influences

- Tower and its geometry
- Foundations
- Optimum spans
- Rating and configuration of Insulator string
- Insulator swings
- Ground clearance
- Line interferences like electric field at ground,
corona, radio & TV interference, audible noise etc

14. CONDUCTOR SELECTION SCENARIOS
Scenario I
Selection of conductor for a transmission line of identified voltage
level and specified minimum power flow but power flow capacity
becomes ruling factor in selection of conductor size (low voltage
lines).

Scenario II
Selection of conductor for a transmission line with identified
voltage level and a specified minimum power flow but voltage
level becomes ruling factor in selection of conductor/conductor
bundle size (EHV/UHV lines).

Scenario III
Selection of conductor for high power capacity long distance
transmission lines where selection of voltage level and
conductor/conductor bundle size are to be done together to
obtain most optimum solution (HVDC Bipole).

15. CONDUCTOR BUNDLE SELECTION:
METHODOLOGY
Preliminary set of conductor bundle/ sizes identified
to start optimization

Parameters like insulation requirements, limits for corona,
RIV,TVI,AN,EF,thermal ratings, line losses and statutory clearances
identified

Detailed analysis of various alternatives in respect of following to be
carried out to select the configuration
- Basic insulation design and insulator selection
- Tower configuration analysis
- Tower weight and foundation cost analysis
- Capital line cost analysis and span optimization
- Line loss calculations
- Economic evaluations (PWRR) of alternatives
- Comparison of interference performance
- Cost sensitivity analysis

16. Conductor Current Carrying Capacity
Conductor Heat Balance
Heat Generated = Heat
Dissipated
Heat Generated = I
2
R +
Solar radiation (q
s)
Heat Dissipated =
Convection Cooling (q
c)+
Radiation Cooling (q
r)
I
2
R = (q
r) + (q
s) - (q
s)
The above equation solved
for conductor temperature
at point of heat balance

CURRENT CARRYING CAPACITY:
VARIATION W.R.T AMBIENT TEMPERATURE
0
200
400
600
800
1000
1200
20253035404550
Ambient Temp (degC)
Current Carrying Capacity
(Amp)
Conductor- ACSR Moose
Max Temp 75deg C
Solar Radiation: 1045 W/sqm
Wind Speed 2Km/hr
Absorption Coeff: 0.8
Emmisitivity coeff: 0.45 Conductor Current Carrying Capacity : Variation w.r.t
Max. Permissible Temp
0
200
400
600
800
1000
1200
1400
65758595115125
Max Permissible Temp (deg C)
Current Carrying Capacity
(degC)
Conductor- ACSR Moose
Ambient Temp: 45 degC
Solar Radiation: 1045 W/sqm
Wind Velocity :2km/hr
Absorption Coeff: 0.8
Emmisitivity Coeff: 0.45

17. CONDUCTOR SURFACE GRADIENT
Conductor Surface gradient depends upon voltage
level, number & dia of conductors, bundle
configuration, phase spacing, clearances etc.

Average Surface gradient E
AVG= Q/ (2r)

Where Q = [C] [V] & r = conductor radius

Maximum Surface gradient E
MAX= E
AVG (1+d(n-1)/D)
Where d = sub conductor diameter
D = conductor bundle diameter
N = number of sub conductors
r=Conductor radius

18. CORONA OR VISIBLE DISCHARGE
Corona discharges form at the surface of the
transmission line conductor when the electric field
intensity (surface gradient) on the conductor surface
exceeds the breakdown strength of the air.

Critical surface voltage gradient
To determine the onset gradient E
peak of a conductor ,
the following formulae is used
E
peak= 31m (1+.308/ r)
m=Surface roughness factor (.9 for dry .6 for rain)
= Relative air density, r=Conductor radius

Corona onset gradient should be greater than max
conductor surface gradient. E
peak> E
MAX

19. INTERFERENCE Produced by Transmission Lines
Electric field at ground

Magnetic field (not a predominant issue for EHV/UHV lines)

Audible Noise

Radio Interference

20. ELECTRIC FIELD
0
2
4
6
8
10
12
0 10 20 30 40 50 60
LATERAL DISTANCE FROM CENTER PHASE (M)
ELECTRIC FIELD (KV/M)
400kV D/C (Twin Moose) 400kV S/C (Twin Moose)
800kV S/C (Quad Bersimis) MAXIMUM EXPOSURE TIME FOR HUMAN BEINGS UNDER VARIOUS
ELECTRIC FIELDS

GRADIENT (KV/M)

TIME (MIN.)
5

Unlimited
10

180
15

90
20

10
25

6

21. AUDIBLE NOISE STUDY RESULTS
40
50
60
5 10 15 20 25 30 35 40
LATERAL DISTANCE FROM OUTER PHASE (M)
Audible Noise L50 (dB above
20 micro pascal)
400KV S/C (Twin Moose) 800KVS/C (Quad Bersimis)
400 KV D/C (Twin Moose) PSYCHOLOGICAL EFFECTS OF AUDIBLE
NOISE
48
50
52
54
56
58
60
AUDIBLE NOISE (dB)
MODERATE
HIGH
LOW
NUMEROUS COMPLAINTS
SOME COMPLAINTS
NO COMPLAINTS RADIO INTERFERENCE STUDY RESULTS
22
24
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
0 10 20 30 40 50 60 70
LATERAL DISTANCE (M)
RI (db/1uV/M at 1MHz)
400 kV , Grd Clearance= 9m 800kv, Grd. Clearance= 23.5m
800kV, Grd. Clearance= 31.5m

22. DESIGN OF TOWERS
Transmission Line Towers are designed as
per IS:802:1995 considering wind zones as
per IS:875:1987

SALIENT DESIGN CONDITIONS

RELIABILITY REQUIREMENTS CLIMATIC LOADS UNDER
NORMAL CONDITION

SECURITY REQUIREMENTS FAILURE CONTAINMENT
LOADS UNDER BROKEN
WIRE CONDITION

SAFETY REQUIREMENTS LOADS DURING CONSTRUC-
TION AND MAINTENANCE
LOAD.

23. Reliability Levels
RELIABILITY RETURN SUGGESTED FOR
LEVEL PERIOD

1 50 FOR EHV TRANS LINES UPTO 400KV
CLASS

2 150 FOR TRANS LINES ABOVE 400KV CLASS
AND TRIPLE & QUAD CIRCUIT TRANS LINE
UPTO 400KV.

3 500 FOR TALL RIVER CROSSING TOWERS AND
SPECIAL TOWERS.

24. TOWER LOADING
Wind Effects:-
i). Basic wind speed
Wind Zone: 1 2 3 4 5 6
Vb(m/sec): 33 39 44 47 50 55
ii). Reference wind speed (Vr=Vb/k0) k0=1.375
iii). Design wind speed
Vd = Vr.K1.K2
Where K1 = risk coefficient factor
k2 = terrain coefficient factor
iv). Design Wind Pressure
0.6 Vd. Vd.

25. Loads Due To Conductor & Earthwire
i). Transverse Load
a). Due to Conductor & Earthwire.
Pd . Cdc. L . Gc. d
b). Due to insulator string. Where,
Cdi. Pd. Ai . Gi Pd = Design wind pressure
c). Deviation loads Cdc, Cdi = Drag co-officients
2T. Sin(D/2) L = Wind span
Gc, Gi = Gust response factors
ii). Vertical Load d = Dia of cable
T = Design tension
iii). Longitudinal Load D = Deviation angle

26. Analysis And Design
ANALYSIS
i). GRAPHICAL METHOD
ii). ANALYTICAL METHOD
iii). COMPUTER AIDED ANALYSIS
(K) (A) = (P)
DESIGN AS COMPRESSION AND TENSION MEMBERS.

CODAL PROVOSION FOR LIMITING SLENDERNESS RATIO FOR
COMPRESSION MEMBER DESIGN
i). LEG MEMBERS - 120
ii). BRACINGS - 200
iii). REDUNDANTS - 250
iv). TENSION MEMBERS - 400

27. NAME, VOLTAGE, CLASS,
WIND ZONE & BASIC DESIGN
PARAMETERS ( FROM
APPROVED FR OR SEF
GROUP)
GEOLOGICAL CONSTRAINTS
DETAILS OF ROUTE & BILL
OF QUANTITIES (FROM SITE)
DESIGN PHILOSPHY (FROM
IS / IEC/ STANDARDISATION
COMMITTEE REPORTS)
REVIEW
INPUTS
CONFOIGURATION & TYPE OF TOWERS
TOWER LOADINGS & CONDITIONS
REVIEW
STURUCTIRAL ANALYSIS
-BY COMPUTER
-BY MANUAL VERIFICATION
REVIEW
FINAL DESIGN (THEORITICAL)
STRUCTURAL DRAWINGS
PROTO MANUFACTURE/ FABRICATION
PROTO TESTING (FULL SCALE)
MODIFY DESIGN
REVIEW
FAILED
DESIGN FINALISED
SUCCESSFUL
DESIGN
STAGES
TESTING &
FINALISATION
FLOW CHART FOR TOWER DESIGN

28. Classification of foundations
Foundations are classified based on soil type and subsoil water level
and listed below
Normal Dry
Sandy dry
Wet
Partially submerged
Fully submerged
Black cotton soil
Dry fissured rock (Under cut type)
Wet fissured rock (Under cut type)
Submerged fissured rock (Under cut type)
Hard rock
Unequal chimney foundations are also povided to minimize the benching and
for water logged area as well

29. Design of Foundations
Following ultimate foundation loads acting at
the tower base (along the tower slope) are
considered
Down thrust (Compression)
Uplift (Tension)
Transverse side thrust
Longitudinal side thrust
•Check for Bearing capacity
•Check for uplift capacity
•Check for overturning
•Check for sliding
Design checks

30. MAXIMUM/ CRITICAL TOWER LOADINGS FROM TOWER DESIGN/ PREVIOUS SIMILAR FDN
DESIGN
, TOWER DIMENSIONS & SLOPE FROM TOWER DESIGN
FOUNDATION LOADINGS
LARGE VARIATION WRT
PREVIOUS SIMILAR DESIGN/ NIT
ESTIMATE ?
END
START
FOUNDATION DESIGN BY COMPUTER /MANUALLY
FOUNDATION DRAWINGS
DESIGN FINALISED
TYPE OF FDN FROM BOQ (SITE INPUT), SOIL
PROPERTIES FROM SPECN/ SOIL INV.
REPORT & CONCRETE PROPERTIES FROM
SPECN
DESIGN PHILOSPHY (FROM IS/ CBIP /
(STANDARDISATION COMMITTEE
REPORTS)
YES YES
INPUTS
FINALISATION
REVIEW
REVIEW
REVIEW
REVIEW
REVIEW
FLOW CHART FOR FOUNDATION DESIGN

31. CAP & PIN DISC INSULATOR
& INSULATOR STRINGS

32. INSULATOR AND INSULATOR STRING DESIGN
Electrical design considerations
Insulation design depends on
- Pollution withstand Capability
Min. nominal creepage dist. = Min nominal specific
creepage dist X highest system voltage phase to phase
of the system
Creepage Distance of insulator string required for different pollution
levels
Pollution
Level

Equiv. Salt Deposit Density
(mg/cm
2)


Min
m
nominal specific
creepage dist (mm/Kv)

Light

0.03 to 0.06

16

Medium

0.10 to 0.20

20

Heavy

0.20 to 0.60

25

Very Heavy

>0.60

31

- Switching/ Lightning Over voltage

33. INSULATOR AND INSULATOR STRING DESIGN
Mechanical design considerations

a) Everyday Loading Condition
Everyday load 20 to 25% of insulator rated strength.

b) Ultimate Loading Condition
Ultimate load on insulator to not exceed 70% of its
rating. This limit corresponds roughly to pseudo-elastic
limit.

c) In addition, capacity of tension insulator strings at least
10 % more than rated tensile strength of the line
conductors.

34. Earthwire
Function
To protect conductor against lightning flashovers
To provide a path for fault current



Maximum allowable fault current (I) through
earthwire mainly depends on

Area of earthwire (A)
Maximum permissible temperature
Time of short circuit (t)

I varies proportional to A and inverse proportion to sqrt (t)

35. HARDWARE FITTINGS
For attachment of insulator string to tower
D-Shackles,Ball clevis, Yoke plate, Chain link
For attachment of insulator string to the conductor
Suspension & tension assembly
Fittings like D-Shackles, Socket clevis, chain link
For protection of insulator string from power follow
current
Arcing Horn
For making electric field uniform and to limit the electric
field at the live end
Corona Control Ring/ Grading Ring
For fine adjustment of conductor sag
Sag Adjustment Plate, Turn Buckle

36. HARDWARE FITTINGS-Design
Suspension Assembly
Shaped to prevent hammering between clamp & conductor
To minimize static & dynamic stress in conductor under various
loading conditions
Minimum level of corona/RIV performance
For slipping of conductor under prescribed unbalanced conditions
between adjacent conductor spans

Tension Assembly
To withstand loads of atleast 95% of conductor UTS
To have conductivity more than that of conductor

Sag Adjustment Plate/ Turn Buckle
To adjust sag upto 150mm in steps of 6mm

Corona Control Ring/ Grading Ring
To cover atleast one live end insulator disc
To cover hardware fittings susceptible for Corona/RIV

37. ACCESSORIES FOR CONDUCTOR &
EARTHWIRE
For joining two lengths of conductor/earthwire
Mid Span Compression joint for Conductor/ earthwire

For repairing damaged conductor
Repair Sleeve

For damping out Aeolian vibrations
Vibration Damper for conductor & earthwire

For maintaining sub conductor spacing along the span
Spacers

For damping out Aeolian vibrations, sub span oscillation and to
maintain sub conductor spacing
Spacer Damper

38. ACCESSORIES FOR CONDUCTOR &
EARTHWIRE- Design
Mid Span Compression joint for Conductor/ earthwire &
Repair Sleeve

To withstand at least loads equivalent to 95% of the
conductor UTS
To have conductivity better than equivalent length of
conductor (99.5% Aluminium)

39. WIND INDUCED VIBRATIONS

 AEOLIAN VIBRATIONS
High frequency, low amplitude vibrations induced by low,
steady & laminar wind

 WAKE INDUCED VIBRATIONS
Low frequency, medium amplitude vibrations induced by high
velocity steady winds on bundle conductors

 GALLOPING
Very low frequency, high amplitude vibrations induced by high
velocity steady winds on conductors with asymmetrical ice
deposit
FACTORS INFLUENCING VIBRATION PERFORMANCE
TYPE , STRANDING & DIA OF CONDUCTOR, EARTHWIRE
 CONDUCTOR/EARTHWIRE TENSION
 SUB-CONDUCTOR SPACING IN BUNDLE CONDUCTORS
 BUNDLE CONFIGURATION

40. VIBRATION CONTROL DEVICES
VIBRATION DAMPERS
Commonly used for
vibration control of single
conductor systems as well as
bundle conductors
alongwith spacers

 SPACER DAMPERS
Used for vibration control of
bundle conductors
(instead of combination of
vibration dampers &
spacers)

41. First 765 kV Single Circuit
Transmission Lines Of
POWERGRID

42. SALIENT DESIGN CONSIDERATIONS & IMPORTANT
PARAMETERS OF 800KV KISHENPUR -MOGA
TRANSMISSION LINE

ELECTRICAL DATA

A). NOMINAL VOLTAGE 765KV

B). MAXIMUM SYSTEM VOLTAGE 800KV

C). LIGHTNING IMPULSE WITHSTAND VOLTAGE 2400kVp

D). POWER FREQUENCY WITHSTAND VOLTAGE (WET) 830 kVrms

E). SWITCHING IMPULSE WITHSTAND VOLTAGE (WET) 1550 kVp

F). MINIMUM CORONA EXTINCTION VOLTAGE (DRY) 510kVrms

G). RIV AT 1 MHZ FOR PHASE TO EARTH VOLTAGE 1000uV
OF 510 kVrms

43. CONDUCTOR BUNDLE SELECTION (800 KV Kishenpur -Moga)

- QUAD ACSR BERSIMIS
STRANDING - 42/4.57 + 7/2.54, DIA - 33.05 MM,
WEIGHT - 2.181 KG/M, UTS - 154KN
SUB-CONDUCTOR SPACING - 457 MM


TOWERS, FOUNDATIONS (800 KV Kishenpur -Moga)


- SELF SUPPORTING TYPE OF TOWERS
- FAMILY SELECTED : 0 DEG, 5 DEG & 15 DEG SUS.
30 DEG & 60 DEG TENSION
- REINFORCED CONCRETE TYPE FOUNDATIONS

44. TOWER ELECTRICAL CLEARANCE (800 KV Kishenpur -Moga)

- ELECTRICAL CLEARANCE OF 1.3M CORRESPONDING TO 50 HZ.
POWER FREQUENCY - TO BE MAINTAINED UNDER 55 DEG.
SWING ANGLE.

- ELECTRICAL CLEARANCE OF 4.4 M CORRESPONDING TO
SWITCHING SURGE LEVELS OF 1.75 p .u. - TO BE MAINTAINED
UNDER 25 DEG. SWING ANGLE.

- ELECTRICAL CLEARANCE OF 5.1 M TO TOP & 5.6 M TO SIDE
(+0.5M ADDED FOR LIVE LINE MAINTENANCE) - TO BE
MAINTAINED UNDER STATIONARY CONDITIONS.

- PHASE CLEARANCE : 15M
- MID SPAN CLEARANCE : 9M
- SHIELDING ANGLE : 20 DEG.
- GROUND CLEARANCE : 15 M
{BASED ON ELECTRICAL FIELD LIMIT OF 10KV/M.(AS PER
IRPA/WHO GUIDELINES}

45. INSULATORS (800KV Kishenpur-Moga)

FOR SUSPENSION TOWERS :

- 0 DEG : DOUBLE SUSPENSION 120KN FOR I STRING (2X40)
(IVI) SINGLE SUSPENSION 210 KN FOR V STRING(2X35 )

- 5 DEG : DOUBLE SUSPENSION 120 KN FOR I STRING (2X40)
(IVI) DOUBLE SUSPENSION 160/210KN FOR V STRING
(2X2X35)


- 15 DEG: DOUBLE SUSPENSION 210 KN (4X35)
(VVV)

FOR TENSION TOWERS :

- QUAD TENSION 210 KN

46. RIGHT OF WAY & INTERFERENCE (Kishenpur -Moga)

- RIGHT OF WAY - 85M
- ELECTRICAL FIELD AT EDGE OF RIGHT OF WAY < 2KV/M
- RI AND AN AT EDGE OF RIGHT OF WAY:

VOLTAGE(kV) ALTITUDE(M) RI (DB) AN(dBA)
(FAIR- (WET-
WEATHER) CONDUCTOR)

800 1000 50.3 58.2
765 1000 48.0 55.9
800 500 48.7 56.5
765 500 46.4 54.2

- RI AND AN LEVELS ARE WITHIN INTERNATIONAL
ACCEPTABLE LIMITS.

47. LOADING CRITERIA (800 KV Kishenpur-Moga)


- WIND ZONE - 4 (47M/SEC BASIC WIND SPEED).
- 150 YEAR RETURN PERIOD. AS PER REVISED IS-802.
- DESIGN WIND PRESSURE ON CONDUCTOR - 1825 Pa
- NARROW FRONT WIND LOADING EQUIVALENT TO
WIND SPEED OF 250 KM/HR. A PPLIED ON TOWER
BODY.
- RULING SPAN - 400 M
- MAXM. WIND SPAN - 400 M
- WEIGHT SPANS -
MAXM - 600M FOR SUSPENSION & 750 M FOR
TENSION TOWERS
MINM - 200M FOR SUSPENSION & -200M FOR
TENSION TOWERS.

48. DESCRIPTION

ALTERNATIVES/PARAMETERS/ RESULTS

Conductor Bundle (I) 8 nos. ACSR types with dia ranging from 30.56mm to 38.2mm. (2) 5 nos.
ACAR types with dia ranging from 30.40mm to 35.80mm. (3) 5 nos. AAAC
types with dia ranging from 31.50mm to 35.8mm.
Spans

300 m,350 m,400 m,450 m,500 m,550 m,600 m
Basic Design Considerations
(A) Wind Zone
(B) Reliability Level
(C) Power Flow
(D) System Voltage


Wind Zone 4 as per IS:875(1987)
2 as per IS:802 (1995)
2500 MW
800kV

Results
(A) Optimum Conductor Bundle
(B) Span
i. Ruling
ii. Maximum Wind Span
iii. Weight Spans
iv. Maximum ratio wind to weight span.


QUAD ACSR BERSIMIS

400 m
400 m
200 to 600 m for suspension towers, -200 to 750 m for tension towers
1.4

Line Parameters
(A) Clearances
i. Live Metal Clearance
ii. Minimum Ground Clearance
iii. Minimum Phase Clearance
(B) Insulator String
i. Suspension Towers
0 deg. (I-V-I)
5 deg.(I-V-I)

15 deg. (V-V-V)
(C) Interference Performance
i. Audible Noise
ii. Radio Interference




5.10 m for switching surge,1.3m for power frequency
15.0m
15.0 m

Double I Suspension with 2x 40 nos, 120 kN disc insulators and single
suspension V string with 35 nos, 210kN disc insulators in each arm.
Double I Suspension with 2x 40 nos, 120 kN disc insulators and double
suspension V string with 2x35 nos, 160/210kN disc insulators in each arm.
Double V Suspension with 2x35 nos, 210kN disc insulators in each arm

58dBA
50 dB/1µV/m at 834 kHz


800KV S/C KISHENPUR-MOGA TRANSMISSION LINE

49. 765 kV S/C Kishenpur-Moga Transmission Line
(Horizontal Configuration)

50. New Generation 765 kV Single
Circuit Transmission Lines Of
POWERGRID

51. Special Features
Delta Configuration with I V I Insulator
Strings
Reduced Right of Way - 64 m (instead
of 85 m for Horizontal Configuration
Lines)

52. ROW = 85 Mts ROW = 64 Mts

53. 765 kV S/C Delta Configuration Transmission
Line

54. 765 KV SUBSTATION AT
SEONI

55. 765 kV S/C Line - ELECTRIC FIELD (kV/m)
0
2
4
6
8
10
12
0 5 101520253035404550
Lateral distance (m )
Electric Field (kV/m)
HORIZONTAL CONFIGURATION
DELTA CONFIGURATION

56. 765 kV S/C Line - RADIO INTERFERENCE (dB/1 micro volt/m)
0
10
20
30
40
50
60
0 5 101520253035404550
Lateral Distance (m )
Radio Interference (dB/1 micro volt/m)
HORIZONTAL CONFIGURATION
DELTA CONFIGURATION

57. 765 kV S/C LINE - AUDIBLE NOISE (L5)
52
53
54
55
56
57
58
59
60
61
0 5101520253035404550
Lateral distance (m )
Audible Noise (dB above 20)
HORIZONTAL CONFIGURATION
DELTA CONFIGURATION

58. 765 kV S/C LINE - AUDIBLE NOISE (L50)
48
49
50
51
52
53
54
55
56
57
58
59
05101520253035404550
Lateral Distance (m )
Audible noise (dB above 20)
HORIZONTAL CONFIGURATION
DELTA CONFIGURATION

59. 765 kV Double Circuit
Transmission Line

60. DESIGN & OPTIMIZATION STUDIES
FOR 765 KV D/C TRANSMISSION LINE

Electrical Line Parameters
(Same as 765 kV S/C)
Nominal Line Voltage: 765kV r.m.s
Maximum Line Voltage: 800kV r.m.s
Switching Impulse Withstand level: 1550 kV peak
Air gap clearances : 5.6 m at 0 deg
4.4 m at swing corresponding
to 2 yr return period
1.3 m at swing corresponding
to 50 yr return period

61. DESIGN & OPTIMIZATION STUDIES
FOR 765 KV D/C TRANSMISSION LINE

Conductor – Bundle Alternatives

Quad ACSR Moose (4* 31.77 mm dia)
Quad ACSR Bersimis (4* 35.05 mm dia)
Quad ACSR Lapwing (4* 38.2 mm dia)
Hexa ACSR Zebra (6* 28.62 mm dia)
Hexa ACSR Cardinal (6* 30.4 mm dia)
Hexa ACSR Moose (6* 31.77 mm dia)

62. DESIGN & OPTIMIZATION STUDIES
FOR 765 KV D/C TRANSMISSION LINE

Alternatives Max. Surface Gradient (kV/cm) Fair Weather Corona Onset Gradient
(kV/cm)
Quad Moose 21.2 20
Quad Bersimis 19.6 19.8
Quad Lapwing 17.9 19.7
Hexa Zebra 17.6 20.1
Hexa Cardinal 16.8 20
Hexa Moose 16.2 20
Conductor Surface Gradients & Corona Onset Gradients
Electric Fields
Alternatives Maximum E.F. Within ROW in kV/m E.F. at ROW edge in kV/m
Quad Moose 9.0 1.6
Quad Bersimis 9.0 1.4
Quad Lapwing 9.3 1.5
Hexa Zebra 10.0 1.9
Hexa Cardinal 10.0 1.9
Hexa Moose 10.0 1.9

63. DESIGN & OPTIMIZATION STUDIES
FOR 765 KV D/C TRANSMISSION LINE

Alternatives RIV at ROW edge in dB/µV/m
Quad Moose 53.8
Quad Bersimis 49.6
Quad Lapwing 45.7
Hexa Zebra 38.9
Hexa Cardinal 37.0
Hexa Moose 35.8
Radio Interference
Alternatives A.N. at L5 LEVEL at ROW edge in
dBA
A.N. at L50 LEVEL at ROW edge in
dBA
Quad Moose 63.8 62.8
Quad Bersimis 63.2 61.6
Quad Lapwing 62.0 59.6
Hexa Zebra 58.5 54.6
Hexa Cardinal 58.1 53.7
Hexa Moose 57.7 52.9
Audible Noise

64. DESIGN & OPTIMIZATION STUDIES
FOR 765 KV D/C TRANSMISSION LINE

Insulator Strings
Conductor Bundle “I” Suspension String insulator rating Tension String insulator rating
HEXA Zebra 2 X 160 ; 2 X 35 nos. 4 X 210 ; 4 X 35 nos.
HEXA Cardinal 2 X 160 ; 2 X 35 nos. 4 X 320 ; 4 X 33 nos.
HEXA Moose 2 X 160 ; 2 X 35 nos. 4 X 320 ; 4 X 33 nos.
Conductor Bundle Estimated Capital Cost (in Rs Lakhs
per km)
Percentage Increase
HEXA Zebra 240 Base
HEXA Cardinal 264 10.0 %
HEXA Moose 278 15.8%
Comparative Capital Cost of Line

65. DESIGN & OPTIMIZATION STUDIES
FOR 765 KV D/C TRANSMISSION LINE

Conductor Bundle Losses (kW/km) at 2500 MVA/ckt
Peak Average
HEXA Zebra 286 115
HEXA Cardinal 245 98
HEXA Moose 232 93
Line Losses
Comparative PWRR
Conductor Bundle PWRR of capital cost of line (in
Rs lakhs/ km)
PWRR of losses (in Rs
lakhs/km)
Total PWRR (in Rs
lakhs/km)
HEXA Zebra 360 390 750
HEXA Cardinal 396 334 730
HEXA Moose 417 317 734

66. 765 KV D/C TOWER CONFIGURATION

67. THANK YOU