design of substation

8/2/2019 Design of Substation

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Design of 400/220kV

Sub-station

S.M. MUJUMDAR

General Manager

(sub-station Engineering)

27th April 2005 Jyoti Structures Ltd.,

Mumbai


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Agenda

Overview of 400kV sub-station

Design Process

Design considerations

Question / Answer


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Imp. considerations in substation design

Safety of personnel and equipment

Reliability and Security

Adherence to

Statutory obligations

I.E. rules, Environmental aspects

Electrical design considerations

Structural design considerations

Ease of maintenance Possibility to Expand


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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.


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System parameters Contd..

Remarks220kV400kVDescriptionSr.

(Line-ground)

(open terminals)

460kV

460kV

530kV

460kV

680kV

520kV

610kV

630kV

iii) One min. power freq.

withstand voltage (dry/wet)-- for lines

-- for CB / Isolator

-- for other equipments

1050kVpii) Switching impulse

withstand voltage (dry/wet)

1050kVp

950kVp1050kVp

1550kVp

1300kVp1425kVp

Rated insulation levels

i) Full wave impulse

withstand voltage

-- for lines

-- for reactor/ Xmer-- for other equipments

11.


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Substation Birds view


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400kV Circuit Breaker


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400kV Isolator


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400kV Current Transformer


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400kV CVT


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400kV Surge Arrester


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Shunt Reactor & NGR


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400/220 kV Auto Transformer


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400kV Bus Post Insulator


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Wave Trap


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Functions of substation equipments

To discharge lightning over voltages and

switching over 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 abnormal

conditions

2. Circuit Breaker

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

FunctionEquipment


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Functions of substation equipments Contd

Compensation of long lines.14. Series Capacitor

To step-up or step-down the voltage and

transfer power from one a.c. voltage another

a.c. voltage at the same frequency.

13. Power Transformer

To provide compensations to reactive loads of

lagging power factors

12. Shunt capacitors

To prevent high frequency signals from entering

other zones.

11. Line Trap

To provide connection between high voltage

line & PLCC equipment

10. Coupling capacitor

To limit earth fault current9. Neutral-Grounding

resistor

To control over voltages by providing reactive

power compensation

8. Shunt reactor


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Functions of Associated system in substation

3. Illumination system (lighting)

-- for switchyard

-- buildings

-- roads etc.

To protect the outdoor substation

equipment from lightning strokes.

2. Overhead earth wire

shielding or Lightning masts.

To provide an earthmat for connecting

neural points, equipment body, support

structures to earth. For safety of

personnel and for enabling earth fault

protection. To provide the path for

discharging the earth currents fromneutrals, faults, Surge Arresters,

overheads shielding wires etc. with safe

step-potential and touch potential.

1. Substation Earthing system

-- Earthmat

-- Earthing spikes

-- Earthing risers

FunctionSystem


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Contd..

To provide alarm or automatic tripping offaulty part from healthy part and also to

minimize damage to faulty equipment and

associated 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 line

carries communication system

-- line trap

-- coupling capacitor

-- PLCC panels

To provide supply path to various

auxiliary equipment and machines.

6. Power cable


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Contd

To sense the occurrence of fire by

sensors and to initiate water spray,

to disconnect power supply to

affected region to pin-point location

of fire by indication 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 external

communication

10. Telephone, telex, microwave,

OPF

For supplying starting power,

standby power for auxiliaries

9. Auxiliary standby power system

-- diesel generator sets

-- switchgear

-- distribution system


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Basic drawings for design/construction

Single Line Diagram

General Arrangement Drawing

Electrical Plan and Section

Control Room Architectural layout


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Supporting drawings

Structural layout

Earthmat layout

Civil layout

Erection Key Diagram

Lighting Layout


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Single Line Diagram 220kV


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General arrangement layout


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Electrical layout


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Electrical Section


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Control room layout


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Control room layout


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Structural layout


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Earthmat Layout

@

@

@

@

@

@

@

@

@


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Civil layout


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Lighting Design

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

activities

Recommended value of Illumination level

Control & Relay panel area - 350 Lux (at floor level)

Test laboratory - 300 Lux

Battery room - 100 Lux

Other indoor area - 150 Lux

Switchyard - 50 Lux (main equipment)

- 20 Lux (balance Area / road @

ground level)


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Single Bus arrangement


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Single Bus System

4. Can be used only where

loads can be interrupted or

have other supply

arrangements.

3. Sectionalizing

increases flexibility

3. Bus cannot be extended

without completely de-

energizing substations

3. Simple Protection

2. Not used for large

substations.

2. Difficult to do any

maintenance

2. Simple to Operate

1. Used for

distribution

substations upto 33kV

1. Fault of bus or any

circuit breaker results in

shut-down of entire

substation

1. Low cost

RemarksDemeritsMerits


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Main & Transfer Bus


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Main & transfer busbar system

3. Fault of bus or any

circuit breaker results in

shutdown of entire

substation.

3. Potential devices may

be used on the main bus

.2. Switching is

somewhat complex

when maintaining a

breaker

2. Any breaker can be

taken out of service for

maintenance.

1. Used for 110kV

substations where cost

of duplicate bus barsystem is not justified

1. Requires one extra

breaker coupler

1. Low initial & ultimate

cost



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Double Busbar arrangement


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Double Bus Bar Single Breaker system

5. Bus couplers failure takes

entire substation out of

service.

4. Line breaker failure takes

all circuits connected to the

bus out of service.

3. High exposure to bus fault.

2. Bus protection scheme

may cause loss of substationwhen it operates.

2. Half of the feeders

connected to each bus

1. Most widely

used for 66kV,

132kv, 220kV and

important 11kv,

6.6kV, 3.3kV

substations.

1. Extra bus-coupler circuit

breaker necessary.

1. High flexibility



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Double Busbar with Double breaker


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Double Bus Bar Double Breaker system

4. High reliability

3. Any breaker can be

taken out of service for

maintenance.

2. Used only for veryimportant, high power,

EHV substations.

2. Would lose half ofthe circuits for breaker

fault if circuits are not

connected to both the

buses.

2. Has flexibility inpermitting feeder

circuits to be connected

to any bus

1. Not used for usual

EHV substations due to

high cost.

1. Most expensive1. Each has two

associated breakers



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Double main & transfer


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Double main bus & transfer bus system

7. Bus fault does not remove any

feeder from the service

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

maintenance.

5. Simple operation, no isolator

switching required

4. All switching done with breakers

3. Breaker failure on bus side

breaker removes only one ckt.From service

2. Highly reliable

1. Preferred by

some utilities for

400kV and

220kV

important

substations.

1. High cost due to

three buses

1. Most flexible in operationRemarksDemeritsMerits


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One & half breaker scheme


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One & half breaker scheme

6. Selective tripping

5. All switching by breaker.

4. Each circuit fed by twobreakers.

3. Requires 1 1/2 breaker per

feeder.

2. Preferred.2. Protection and

auto-reclosing morecomplex since

middle breaker must

be responsive to

both associated

circuits.

2. Any breaker can be removed

from maintenance withoutinterruption of load.

1. Used for 400kV

& 220kV

substations.

1. One and half

breakers per circuit,

hence higher cost

1. Flexible operation for breaker

maintenance



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Ring Bus


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Mesh (Ring) busbar system

4. Breaker failure during fault on one

circuit causes loss of additional

circuit because of breaker failure.

3. Requires VTs on all circuits

because there is no definite voltage

reference point.

These VTs may be required in all

cases for synchronizing live line orvoltage indication

2.Auto-reclosing and protection

complex.

1. Most widely

used for very

large power

stations having

large no. ofincoming and

outgoing lines

and high power

transfer.

1. If fault occurs during bus

maintenance, ring gets separated

into two sections.

1. Busbars gave

some operational

flexibility



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Minimum Clearances

4300 mm6400 mm3. Sectional clearance

2100 mm4200 mm

(Rod-conductor configuration)

4000 mm

(Conductor-conductor configuration)

2. Phase to phase

2100 mm3500 mm1. Phase to Earth

220kV400kV


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Clearance Diagram


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Bus Bar Design

Continuous current rating. Ampacity caculation 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


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Gantry Structure Design

ClearancesNo windMax.

(ACSR 750C/ AAAC 850C)

5.

T


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Contd..

Short Circuit Forces calculation

As per IEC : 865

Short circuit forces during short circuit

Short circuit forces after short circuit

Short circuit forces due to Pinch effect for Bundled conductor

Spacer span calculation

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

circuit condition


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spacers


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Spacer span Vs Short Ckt. forces

GRAPH OF SPACER SPAN Vs CONDUCTOR TENSION FOR

400 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.

CONDUC

TOR

TENSION

PER

PHASE

INK

G.


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Earthing Design

Guiding standards IEEE 80, IS:3043, CBIP-223.

400kV & 220kV system are designed for 40kA.

Basic Objectives:

Step potential within tolerable

Touch Potential limit

Ground Resistance

Adequacy of Ground conductor for fault current

(considering corrosion)


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Touch and step potential


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Lightning Protection Ground Wire

FIG-4bFIG-4a


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Lightning Protection Lightning Mast


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design of substation

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