800 kV TL Design

DESIGN & OPTIMIZATIONOF 800 KV TRANSMISSION

LINE

Gopal JiAGM (Engineering TL Dept.)

Power Grid Corporation of India limited

Gurgaon, India

MAJOR COMPONENTS OF A TRANSMISSION LINE

ConductorTowers (and Foundations)EarthwireInsulators ] InsulatorHardware Fittings ] stringsAccessories

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

Review ofExisting 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

DESIGN AND OPTIMISATION OF POWER TRANSMISSION LINES

Review of existing system and practicesSelection of clearancesInsulator and insulator string design

InsulatorHardware

Bundle conductor studiesTower configuration analysisTower weight estimationFoundation volumes estimationLine cost analysis & span optimizationEconomic evaluation of line

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

SELECTION OF CLEARANCES

Tower Clearance (Strike Distance) for different swing anglesPhase to Phase Spacing Ground ClearanceMid Span Clearance and Shielding AngleRight of Way Clearance

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

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

MAX

M.

SAG

=14.

5 M

21.5 sin 55 = 17.50 M

9.0 M elect. Clearance required as per IE Rules

MIN

. GRO

UND

CLEA

RANC

E=15

M

55 degswing

Insulator string

Max

imum

sag

of

cond

ucto

r

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.

Ove

r V

olta

ge

Prob

abil

ity

Den

sity

Insu

lati

on F

lash

over

Pr

obab

ilit

y

Voltage-kV

Stress

StrengthHow many Flashovers?

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.

TYPICAL POWER FREQUENCY AC FLASHOVER CHARACTERISTICS OF LARGE AIR GAPS

0

5001000

15002000

2500

1 2 3 4 5 6

Gap Spacing,m

Criti

cal F

lash

over

Vol

tage

(C

rest

),kV

Rod to PlaneInsulator stringConductor to Tower LegConductor to ConductorVertical Rod to Rod

TYPICAL AIR GAP SWITCHING SURGE CFO's

0

500

1000

1500

2000

2500

3000

3 4 6 8 10 12

Gap Spacing,m

Cri

tical

Fla

sh

over

Vo

ltag

e,k

V

Rod to PlaneTower WindowHorizontal Rod to Rod

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

CONDUCTOR SELECTION SCENARIOS

Scenario ISelection 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 IIISelection 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).

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

Conductor Current Carrying Capacity

Conductor Heat BalanceHeat Generated = Heat DissipatedHeat Generated = I2R + Solar radiation (qs)

Heat Dissipated = Convection Cooling (qc)+ Radiation Cooling (qr)

I2R = (qr) + (qs) - (qs)

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

20 25 30 35 40 45 50

Ambient Temp (degC)

Cur

rent

Car

ryin

g C

apac

ity

(Am

p)

Conductor- ACSR MooseMax Temp 75deg CSolar Radiation: 1045 W/sqmWind Speed 2Km/hrAbsorption Coeff: 0.8Emmisitivity coeff: 0.45

Conductor Current Carrying Capacity : Variation w.r.t Max. Permissible Temp

0

200

400

600

800

1000

1200

1400

65 75 85 95 115 125

Max Permissible Temp (deg C)

Cur

rent

Car

ryin

g C

apac

ity

(deg

C)

Conductor- ACSR MooseAmbient Temp: 45 degCSolar Radiation: 1045 W/sqmWind Velocity :2km/hrAbsorption Coeff: 0.8Emmisitivity Coeff: 0.45

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/ (2r)

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

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 gradientTo determine the onset gradient E peak of a conductor , the following formulae is usedE 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

INTERFERENCE Produced by Transmission Lines

Electric field at ground

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

Audible Noise

Radio Interference

ELECTRIC FIELD

0

2

4

6

8

10

12

0 10 20 30 40 50 60

LATERAL DISTANCE FROM CENTER PHASE (M)

EL

EC

TR

IC F

IEL

D (

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 Unlimited10 18015 9020 1025 6

AUDIBLE NOISE STUDY RESULTS

40

50

60

5 10 15 20 25 30 35 40

LATERAL DISTANCE FROM OUTER PHASE (M)

Aud

ible

Noi

se L

50 (d

B a

bove

20

mic

ro p

asca

l)

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

AU

DIB

LE N

OIS

E (d

B)

MODERATE

HIGH

LOW

NUMEROUS COMPLAINTS

SOME COMPLAINTS

NO COMPLAINTS

RADIO INTERFERENCE STUDY RESULTS

222426283032343638404244464850525456

0 10 20 30 40 50 60 70LATERAL DISTANCE (M)

RI (d

b/1

uV

/M a

t 1

MH

z)

400 kV , Grd Clearance= 9m 800kv, Grd. Clearance= 23.5m

800kV, Grd. Clearance= 31.5m

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 UNDERNORMAL CONDITION

SECURITY REQUIREMENTS FAILURE CONTAINMENTLOADS UNDER BROKENWIRE CONDITION

SAFETY REQUIREMENTS LOADS DURING CONSTRUC-TION AND MAINTENANCE LOAD.

Reliability Levels

RELIABILITY RETURN SUGGESTED FORLEVEL 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.

TOWER LOADING

Wind Effects:-i). Basic wind speedWind Zone: 1 2 3 4 5 6Vb(m/sec): 33 39 44 47 50 55ii). Reference wind speed (Vr=Vb/k0) k0=1.375iii). Design wind speed

Vd = Vr.K1.K2Where K1 = risk coefficient factor

k2 = terrain coefficient factoriv). Design Wind Pressure

0.6 Vd. Vd.

Loads Due To Conductor & Earthwire

i).Transverse Loada). 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

Analysis And Design

ANALYSISi). GRAPHICAL METHODii). ANALYTICAL METHODiii). COMPUTER AIDED ANALYSIS(K) (A) = (P)DESIGN AS COMPRESSION AND TENSION MEMBERS.

CODAL PROVOSION FOR LIMITING SLENDERNESS RATIO FOR COMPRESSION MEMBER DESIGNi). LEG MEMBERS - 120ii). BRACINGS - 200

iii). REDUNDANTS - 250 iv). TENSION MEMBERS - 400

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 & CONDITIONSREVIEW

STURUCTIRAL ANALYSIS -BY COMPUTER

-BY MANUAL VERIFICATION

REVIEW

FINAL DESIGN (THEORITICAL)

STRUCTURAL DRAWINGS

PROTO MANUFACTURE/ FABRICATION

PROTO TESTING (FULL SCALE)

MODIFY DESIGN

REVIEW

FAILEDDESIGN FINALISED

SUCCESSFUL

DESIGN STAGES

TESTING & FINALISATION

FLOW CHART FOR TOWER DESIGN

Classification of foundationsFoundations are classified based on soil type and subsoil water level and listed belowNormal Dry Sandy dryWetPartially submergedFully submergedBlack cotton soilDry 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

Design of FoundationsFollowing ultimate foundation loads acting at the tower base (along the tower slope) are considered

Down thrust (Compression)Uplift (Tension)Transverse side thrustLongitudinal side thrust

•Check for Bearing capacity•Check for uplift capacity•Check for overturning•Check for sliding

Design checks

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

CAP & PIN DISC INSULATOR & INSULATOR STRINGS

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 systemCreepage Distance of insulator string required for different pollution levels

PollutionLevel

Equiv. Salt Deposit Density (mg/cm2)

Minm 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

INSULATOR AND INSULATOR STRING DESIGN Mechanical design considerations

a) Everyday Loading ConditionEveryday 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.

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)

HARDWARE FITTINGS

For attachment of insulator string to towerD-Shackles,Ball clevis, Yoke plate, Chain link

For attachment of insulator string to the conductor

Suspension & tension assemblyFittings 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 sagSag Adjustment Plate, Turn Buckle

HARDWARE FITTINGS-Design

Suspension AssemblyShaped to prevent hammering between clamp & conductorTo minimize static & dynamic stress in conductor under various loading conditionsMinimum level of corona/RIV performanceFor slipping of conductor under prescribed unbalanced conditions between adjacent conductor spans

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

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

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

ACCESSORIES FOR CONDUCTOR & EARTHWIRE

For joining two lengths of conductor/earthwireMid Span Compression joint for Conductor/ earthwire

For repairing damaged conductorRepair Sleeve

For damping out Aeolian vibrationsVibration Damper for conductor & earthwire

For maintaining sub conductor spacing along the spanSpacers

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

Spacer Damper

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 UTSTo have conductivity better than equivalent length of conductor (99.5% Aluminium)

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

VIBRATION CONTROL DEVICES

VIBRATION DAMPERSCommonly used for vibration control of single conductor systems as well as bundle conductors alongwith spacers

SPACER DAMPERSUsed for vibration control of bundle conductors(instead of combination of vibration dampers & spacers)

First 765 kV Single Circuit Transmission Lines Of

POWERGRID

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

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

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}

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

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.

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. APPLIED 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.

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 MW800kV

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 m400 m200 to 600 m for suspension towers, -200 to 750 m for tension towers1.4

Line Parameters(A) Clearancesi. Live Metal Clearanceii. Minimum Ground Clearanceiii. Minimum Phase Clearance(B) Insulator Stringi. Suspension Towers 0 deg. (I-V-I) 5 deg.(I-V-I) 15 deg. (V-V-V) (C) Interference Performance i. Audible Noiseii. Radio Interference

5.10 m for switching surge,1.3m for power frequency15.0m15.0 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 58dBA50 dB/1µV/m at 834 kHz

800KV S/C KISHENPUR-MOGA TRANSMISSION LINE

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

New Generation 765 kV Single Circuit Transmission Lines Of POWERGRID

Special Features

Delta Configuration with I V I Insulator StringsReduced Right of Way - 64 m (instead of 85 m for Horizontal Configuration Lines)

ROW = 85 Mts ROW = 64 Mts

765 kV S/C Delta Configuration Transmission Line

765 KV SUBSTATION AT SEONI

765 kV S/C Line - ELECTRIC FIELD (kV/m)

0

2

4

6

8

10

12

0 5 10 15 20 25 30 35 40 45 50

Lateral distance (m)

Ele

ctri

c F

ield

(kV

/m)

HORIZONTAL CONFIGURATION

DELTA CONFIGURATION

765 kV S/C Line - RADIO INTERFERENCE (dB/1 micro volt/m)

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40 45 50

Lateral Distance (m)

Rad

io In

terf

eren

ce (

dB

/1 m

icro

vo

lt/m

)


DELTA CONFIGURATION

765 kV S/C LINE - AUDIBLE NOISE (L5)

52

53

54

55

56

57

58

59

60

61

0 5 10 15 20 25 30 35 40 45 50

Lateral distance (m)

Aud

ible

Noi

se (d

B a

bove

20)


DELTA CONFIGURATION

765 kV S/C LINE - AUDIBLE NOISE (L50)

48

49

50

51

52

53

54

55

56

57

58

59

0 5 10 15 20 25 30 35 40 45 50

Lateral Distance (m)

Au

dib

le n

ois

e (d

B a

bo

ve 2

0)


DELTA CONFIGURATION

765 kV Double Circuit Transmission Line

DESIGN & OPTIMIZATION STUDIESFOR 765 KV D/C TRANSMISSION LINE

Electrical Line Parameters(Same as 765 kV S/C)

Nominal Line Voltage: 765kV r.m.sMaximum Line Voltage: 800kV r.m.sSwitching Impulse Withstand level: 1550 kV peakAir gap clearances : 5.6 m at 0 deg

4.4 m at swing corresponding to 2 yr return period

1.3 m at swing correspondingto 50 yr return period


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)


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



Hexa Zebra 10.0 1.9

Hexa Cardinal 10.0 1.9

Hexa Moose 10.0 1.9


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



Hexa Zebra 58.5 54.6

Hexa Cardinal 58.1 53.7

Hexa Moose 57.7 52.9

Audible Noise


Insulator StringsConductor 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


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

765 KV D/C TOWER CONFIGURATION

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800 kV TL Design

Documents

db1 micro

conductorconductor

210kn disc

live metal

minimum power

identified

conductor

audible noise