400-200 kV Substation Design

“Design of 400/220kVSub-station”

S.M. MUJUMDARGeneral Manager(sub-station Engineering)

27th April 2005 Jyoti Structures Ltd., Mumbai

Agenda

Overview of 400kV sub-station

Design Process

Design considerations

Question / Answer

Imp. considerations in substation design

Safety of personnel and equipmentReliability and SecurityAdherence to

Statutory obligations– I.E. rules, Environmental aspectsElectrical design considerationsStructural design considerations

Ease of maintenancePossibility to Expand

System parameters

1000 mV(156kV)

1000 mV(320kV)

Radio interference voltage at 1MHZ(for phase to earth voltage)

10.

40kA40kARated short ckt. Current for 1 sec.8.

25mm/kV25mm/kVMin. Creepage distance7.

156kV320kVCorona Extinction voltage6.

Effectively earthedSystem neutral earthing5.

33Number of phases4.

50Hz50HzRated frequency3.

245kV420kVMax. operating voltage2.

220kV400kVNominal system voltage1.

220kV400kVDescriptionSr.

System parameters Contd..

Remarks220kV400kVDescriptionSr.

(Line-ground)(open terminals)

460kV460kV530kV460kV

680kV520kV610kV630kV

iii) One min. power freq.withstand voltage (dry/wet)

-- for lines-- for CB / Isolator

-- for other equipments

1050kVpii) Switching impulsewithstand voltage (dry/wet)

1050kVp950kVp1050kVp

1550kVp1300kVp1425kVp

Rated insulation levelsi) Full wave impulsewithstand voltage

-- for lines-- for reactor/ X’mer-- for other equipments

11.

Substation Bird’s view

400kV Circuit Breaker

400kV Isolator

400kV Current Transformer

400kV CVT

400kV Surge Arrester

Shunt Reactor & NGR

400/220 kV Auto Transformer

400kV Bus Post Insulator

Wave Trap

Functions of substation equipments

To discharge lightning over voltages and switchingover voltages to earth

7. Lightning Arrester

To step-down voltages for measurement, control &protection

6. Voltage Transformer

To step-down currents for measurement, control &protection

5. Current Transformer

To discharge the voltage on dead lines to earth4. Earthing switch

Disconnection under no-load condition for safety,isolation and maintenance.

3. Isolators

Automatic switching during normal or abnormalconditions

2. Circuit Breaker

Incoming & outgoing ckts. Connected to bus-bar1. Bus-Bar

FunctionEquipment

Functions of substation equipments Contd…

Compensation of long lines.14. Series Capacitor

To step-up or step-down the voltage and transferpower from one a.c. voltage another a.c. voltageat the same frequency.

13. Power Transformer

To provide compensations to reactive loads oflagging power factors

12. Shunt capacitors

To prevent high frequency signals from enteringother zones.

11. Line –Trap

To provide connection between high voltage line &PLCC equipment

10. Coupling capacitor

To limit earth fault current9. Neutral-Groundingresistor

To control over voltages by providing reactivepower compensation

8. Shunt reactor

Functions of Associated system in substation

3. Illumination system (lighting)-- for switchyard-- buildings-- roads etc.

To protect the outdoor substationequipment from lightning strokes.

2. Overhead earth wire shieldingor Lightning masts.

To provide an earthmat for connectingneural points, equipment body, supportstructures to earth. For safety of personneland for enabling earth fault protection. Toprovide the path for discharging the earthcurrents from neutrals, faults, SurgeArresters, overheads shielding wires etc.with safe step-potential and touchpotential.

1. Substation Earthing system-- Earthmat-- Earthing spikes-- Earthing risers

FunctionSystem

Contd..To provide alarm or automatic tripping offaulty part from healthy part and also tominimize damage to faulty equipment andassociated system.

4. Protection system-- protection relay panels-- control cables-- circuit breakers-- CTs, VTs etc.

For Protective circuits, control circuits,metering circuits, communication circuits

5. Control cable

For communication, telemetry, tele-control,power line carrier protection etc.

7. PLCC system power linecarries communication system

-- line trap-- coupling capacitor-- PLCC panels

To provide supply path to various auxiliaryequipment and machines.

6. Power cable

Contd…To sense the occurrence of fireby sensors and to initiate waterspray, to disconnect powersupply to affected region to pin-point location of fire byindication in control room.

8. Fire Fighting system-- Sensors, detection system-- water spray system-- fire prot. panels, alarm

system-- watertank and spray system

For internal and externalcommunication

10. Telephone, telex,microwave, OPF

For supplying starting power,standby power for auxiliaries

9. Auxiliary standby powersystem

-- diesel generator sets-- switchgear-- distribution system

Basic drawings for design/construction

Single Line Diagram

General Arrangement Drawing

Electrical Plan and Section

Control Room Architectural layout

Supporting drawings

Structural layout

Earthmat layout

Civil layout

Erection Key Diagram

Lighting Layout

Single Line Diagram – 220kV

General arrangement layout

Electrical layout

Electrical Section

Control room layout

Structural layout

Earthmat Layout

@

@

@

@

@

@

@

@

@

Civil layout

Erection Key Diagram

EW 2E W 2

4 S14 S1

4 D T T M -2

EW 1

4 I4 S1

4 LA 4 P 4 V4 S1 4 W4 W

4 S14 S1

4 I

4 S1

4 LA4 S 1

R 1

4 SST M -D

4 T 14 T 14 T 1

4 S1 4 S14 S1

EW 2EW 2

4 S14 S 1

4 S1

4 D T T M -1 4 S24 S2 4 S2

EW 1

4 SST M -D

4 T B SM4 T B SM 4 T B SM

4 P 14 I4 P 34 S1 4 S1

4 P 14 I4 I C1

4 S1 4 S14 S1

4 B4 I2 4 I14 I4 I C2

4 S1

4 C24 C1 4 I 14 B

EW 2EW 2

4 SST M -T

4 S2 4 S24 T M

4 S1 4 S14 S1

4 D T T M -14 D T T M -2

E W 1

4 S24 S2 4 S2

4 I 2

4 S1

4 IC2

4 D T T M -1

4 D T T M -1

4 D T T M -1

4 D T T M -1

4 D T T M -1

4 D T T M -1

4SST

M-D4L

A

4P4P

4P4LA

4LA

4W4V4V

4V 4W

4SST

M-D

4 D T T M -1

4 D T T M -1

4 D T T M -1

4SST

M-D

4I4I

4I4I

4I 4I

4W4P 4V4LA

4P4LA

4V

4P4LA

4V 4W

4SST

M-D

4 D T T M -1

4 D T T M -1

4SST

M-D

4I4I

4I4I

4 D T T M -1

4I

4SST

M-D

4I

4P3

R1R1

R1 4LA

4LA

4LA

4 D T T M -2

4P3

4P3

4I4I

4I

4 D T T M -2

4I4I

4 D T T M -2

4I

R1R1

R1

4LA

4LA

4LA

4P3

4P3

4I4I

4 D T T M -2

4 D T T M -2

4I4I

4P3

4I

4 D T T M -2

4I

4B

4B

4B

4 D T Q B-24 D T Q B-2 4 D T Q B-2

4I2

4I1

4I

4P1

4IC2

4P1

4IC1 4I

2

4I1

4I1

4B

4B

4B

4C2

4C1

4I1

4I2

4C2

4C1

4I1

4I2

4C2

4C1

4I1

4I2

4B

4B

4B

4P1

4I2

4I14IC2

4P1

4IC1

4I2

4I1

4I

4 D T Q B-14 D T Q B-1 4 D T Q B-1

4I1

4C2

4C1

4I1

4B

4I2

4B

4C2

4C1

4I1

4I2

4B

4C1

4C2

4I1

4I2

4W1

4W1

4W1

4W1

4W1

4W1

4W1

4W1

4W1

4W1

N1

R2

R2

N1

Lighting Design

Adequate lighting is necessary for safety of working personnel and O&Mactivities

Recommended value of Illumination levelControl & Relay panel area - 350 Lux (at floor level)Test laboratory - 300 LuxBattery room - 100 LuxOther indoor area - 150 LuxSwitchyard - 50 Lux (main equipment)

- 20 Lux (balance Area / road @ground level)

Single Bus arrangement

Single Bus System

4. Can be used only whereloads can be interrupted orhave other supplyarrangements.

3. Sectionalizingincreases flexibility

3. Bus cannot be extendedwithout completely de-energizing substations

3. Simple Protection

2. Not used for largesubstations.

2. Difficult to do anymaintenance

2. Simple to Operate

1. Used for distributionsubstations up to 33kV

1. Fault of bus or any circuitbreaker results in shut-downof entire substation

1. Low cost

RemarksDemeritsMerits

Main & Transfer Bus

Main & transfer Busbar system

3. Fault of bus or anycircuit breaker resultsin shutdown of entiresubstation.

3. Potential devicesmay be used on themain bus

.2. Switching issomewhat complexwhen maintaining abreaker

2. Any breaker can betaken out of servicefor maintenance.

1. Used for 110kVsubstations wherecost of duplicate busbar system is notjustified

1. Requires one extrabreaker coupler

1. Low initial &ultimate cost


Double Busbar arrangement

Double Bus Bar Single Breaker system

5. Bus couplers failuretakes entire substation outof service.

4. Line breaker failuretakes all circuits connectedto the bus out of service.

3. High exposure to busfault.

2. Bus protection schememay cause loss ofsubstation when itoperates.

2. Half of the feedersconnected to eachbus

1. Most widelyused for 66kV,132kv, 220kVand important11kv, 6.6kV,3.3kVsubstations.

1. Extra bus-coupler circuitbreaker necessary.

1. High flexibility


Double Busbar with Double breaker

Double Bus Bar Double Breaker system

4. High reliability

3. Any breaker canbe taken out ofservice formaintenance.

2. Used only for veryimportant, highpower, EHVsubstations.

2. Would lose half ofthe circuits forbreaker fault if circuitsare not connected toboth the buses.

2. Has flexibility inpermitting feedercircuits to beconnected to any bus

1. Not used for usualEHV substations dueto high cost.

1. Most expensive1. Each has twoassociated breakers


Double main & transfer

Double main bus & transfer bus system

7. Bus fault does not remove anyfeeder from the service

6. Either main bus can be taken outof service at any time formaintenance.

5. Simple operation, no isolatorswitching required

4. All switching done with breakers

3. Breaker failure on bus side breakerremoves only one ckt. From service

2. Highly reliable

1. Preferred bysome utilities for400kV and220kV importantsubstations.

1. High cost due tothree buses

1. Most flexible in operation


One & half breaker scheme

One & half breaker scheme

6. Selective tripping

5. All switching by breaker.

4. Each circuit fed by twobreakers.

3. Requires 1 1/2 breaker perfeeder.

2. Preferred.2. Protection andauto-reclosing morecomplex since middlebreaker must beresponsive to bothassociated circuits.

2. Any breaker can be removedfrom maintenance withoutinterruption of load.

1. Used for 400kV& 220kVsubstations.

1. One and halfbreakers per circuit,hence higher cost

1. Flexible operation for breakermaintenance


Ring Bus

Mesh (Ring) Busbar system

4. Breaker failure during fault on onecircuit causes loss of additional circuitbecause of breaker failure.

3. Requires VT’s on all circuitsbecause there is no definite voltagereference point.These VT’s may be required in allcases for synchronizing live line orvoltage indication

2.Auto-reclosing and protectioncomplex.

1. Most widelyused for verylarge powerstations havinglarge no. ofincoming andoutgoing linesand high powertransfer.

1. If fault occurs during busmaintenance, ring gets separated intotwo sections.

1. Busbars gavesome operationalflexibility


Minimum Clearances

4300 mm6400 mm3. Sectionalclearance

2100 mm4200 mm(Rod-conductor configuration)4000 mm(Conductor-conductorconfiguration)

2. Phase to phase

2100 mm3500 mm1. Phase to Earth

220kV400kV

Clearance Diagram

Bus Bar Design

Continuous current rating. Ampacity calculation as per IEEE:738

Short time current rating (40kA for 1 Sec.) IEC-865

Stresses in Tubular Busbar

Natural frequency of Tubular Busbar

Deflection of Tube

Cantilever strength of Post Insulator

Aeolian Vibrations

Gantry Structure Design

ClearancesNo windMax.(ACSR 750C/ AAAC 850C)

5.

T <= 70% of UTS100%Every Day4.

T <= 22% of UTSNo windEvery Day3.

36%Min.2.

No windMin.1.

LimitsWind PressureTempSr.

Sag / Tension calculation : as per IS: 802 1995

Contd..

Short Circuit Forces calculationAs per IEC : 865

Short circuit forces during short circuitShort circuit forces after short circuitShort circuit forces due to “Pinch” effect for Bundled conductorSpacer span calculation

Factor of safety of 2.0 under normal condition and 1.5 under short circuitcondition

spacers

Spacer span Vs Short Ckt. forces

GRAPH OF SPACER SPAN Vs CONDUCTOR TENSION FOR400 KV TWIN MOOSE ACSR CONDUCTOR

0.00

2000.00

4000.00

6000.00

8000.00

10000.00

12000.00

0 2 4 6 8 10 12 14

SPACER SPAN IN MTRS.

COND

UCTO

R TE

NSIO

N PE

R P

HASE

IN K

G.

Earthing Design

Guiding standards – IEEE 80, IS:3043, CBIP-223.400kV & 220kV system are designed for 40kA.Basic Objectives:

Step potential within tolerableTouch Potential limitGround ResistanceAdequacy of Ground conductor for fault current (consideringcorrosion)

Touch and step potential

Lightning Protection – Ground Wire

FIG-4bFIG-4a

Lightning Protection – Lightning Mast

400-200 kV Substation Design

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