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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
)
HORIZONTAL CONFIGURATION
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)
HORIZONTAL CONFIGURATION
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)
HORIZONTAL CONFIGURATION
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
DESIGN & OPTIMIZATION STUDIESFOR 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)
DESIGN & OPTIMIZATION STUDIESFOR 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
DESIGN & OPTIMIZATION STUDIESFOR 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
DESIGN & OPTIMIZATION STUDIESFOR 765 KV D/C TRANSMISSION LINE
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
DESIGN & OPTIMIZATION STUDIESFOR 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
765 KV D/C TOWER CONFIGURATION
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