Sub Station Abstracts-(Part-1)

SUB STATION ABSTRACTS

SUB STATION EQUIPMENTS AND SAFETY CLEARANCE

RATING OF LIGHTING ARRESTOR:

Size of L.A = 1.5 X Phase to Earth Voltage OR * Size of L.A =1.5 X system Voltage/1.732 OR * Size of L.A = 0.81 X highest System Voltage

LIGHTING ARRESTOR PROTECTION RADIUS:

Protection Radius (Rp) = Sqrt (H X (2D-H)+L(2D+L)) * H= Actual Height of L.A * D= 20 meter, 40 meter or 60 meter * L= V X T (T=Discharge Time & V= 1m/ms)

CREEPAGE DISTANCE:

18 mm to 22 mm /KV for Moderate Polluted Air. * 25 mm to 33 mm /KV for Heavily Polluted Air. * In HVDC System The value is double from above value.

LIGHTING ARRESTOR RATING:

Rated Voltage

Highest Voltage

L.A Rating

132kv

145kv

120kv To 132kv

220kv

245kv

198kv To 216kv

400kv

420kv

336kv

LOCATION OF LIGHTING ARRESTOR:

Rated Voltage

Max Distance from Equipment

132kv

35 meter To 45 meter

220kv

Closed To Transformer

400kv

Closed To Transformer

SIZE OF CORONA RING:

Rated Voltage

Size of Corona Ring

Less than 170 KV

160mm Ring Put on HV end

170KV To 275KV

350mm Ring Put on HV end

More than 275KV

450mm Ring Put on HV end

More than 275KV

350mm Ring Put on HV end

CAPACITY OF SUB STATION AS PER GERC:

Size of S/S

Electrical Load

66 KV

80 MVA

132 KV

150 MVA

220 KV

320 MVA

400 KV

1000 MVA

BREAKING / SHORT CIRCUIT CAPACITY OF SUB STATION:

Size of S/S

Short Circuit Current

66 KV

25 KAmp for 1 or 3 sec

132 KV

31.5 KAmp for 1 or 3 sec

220 KV

40 KAmp for 1 or 3 sec

400 KV

40 KAmp for 1 or 3 sec

FAULT CLEAR TIME:

Size of S/S

Fault Clear Time

66 KV

300 mili Sec

132 KV

160 mili Sec

220 KV

120 mili Sec

400 KV

100 mili Sec

NORMAL TYPE OF CONDUCTORS:

Voltage

Main Bus

Auxiliary Bus

11KV

Twin ACSR Zebra

ACSR Zebra

33KV

ACSR Zebra

132KV

ACSR Zebra

ACSR Panthers

220KV

Twin ACSR Zebra

ACSR Zebra

400KV

1/14.2 mm Dia Alu Pipe

Twin ACSR Moose

NUMBER OF DISC INSULATOR:

System

Number

Strength (KN)

11KV

120KN

33KV

120KN

132KV

120KN

220KV

70KN

220KV (Anti Fog)

2 X 15

120KN

400KV (Anti Fog)

2 X 25

120KN

MINIMUM CLEARANCE:

Voltage

Phase to Earth Wire

Phase to Phase

Section Clearance

2.2KV

28cm

33cm

27.45cm

33KV

380cm

43cm

27.7cm

132KV

107cm

12cm

25cm

220KV

178cm

20.6cm

42.8cm

400KV

350cm

40cm

65cm

GROUND CLEARANCE:

Voltage

Meter

33KV

3.7meter

66 KV

6.1meter

132 KV

6.1meter

220 KV

7.0meter

400 KV

8.8meter

CONDUCTOR SPACING:

Voltage

Highest Voltage

Lighting Impulse Level (Kvp)

Min Clearance

Ground Clearance

Safety working Clearance

Phase to Earth

Phase to Phase

11KV

12kv

178mm

229mm

3700mm

2600mm

33KV

36kv

170

320mm

3700mm

2800mm

132 KV

145kv

550

1300mm

4600mm

3700mm

220 KV

245kv

950

2100mm

5500mm

4300mm

400 KV

420kv

1425

3400mm

4200mm

8000mm

6400mm

EARTHING RESISTANCE VALUE:

Particular

Max Earthing Resistance

Power Station

0.5Ω

EHT Sub Station

1Ω

33KV Sub Station

2Ω

Double Pole Structure

5Ω

Tower foot Resistance

10Ω

Distribution Transformer

5Ω

220KV Sub Station

1Ω To 2Ω

400KV Sub Station

0.5Ω

LOSSES IN 11 KV TRANSFORMER AT 75C (AS PER CBIP):

Transformer

No Load Loss(kw)

Load Loss (kw)

% Impedance

3.15MVA

2.9

6.25

4MVA

3.2

7.15

5.3MVA

3.9

7.15

6.3MVA

4.5

7.15

LOSSES IN 66 KV TRANSFORMER AT 75C (AS PER CBIP):

Transformer

No Load Loss(kw)

Load Loss (kw)

% Impedance

6.3MVA

8.35

8MVA

7.1

8.35

10MVA

8.4

8.35

12.5MVA

9.7

8.35

20MVA

102

10.0

STANDARD RATING OF 66KV TRANSFORMER (AS PER CBIP):

Transformer

Type of Cooling

6.3MVA

66KV/11KV

ONAN

8MVA

66KV/11KV

ONAN

10MVA

66KV/11KV

ONAN

12.5MVA

66KV/11KV

ONAN / ONAF

20MVA

66KV/11KV

ONAN / ONAF

% IMPEDANCE FOR TRANSFORMER (AS PER IS 2026):

33KV Transformer

66KV Transformer

MVA

%Impedance

MVA

%Impedance

1MVA

6.3MVA

8.35%

1.6MVA

6.25%

8MVA

8.35%

3.15MVA

6.25%

10MVA

8.35%

4MVA

7.15%

12.5MVA

8.35%

5MVA

7.15%

20MVA

10%

6.3MVA

7.15%

16MVA

10%

8MVA

8.35%

25MVA

10%

10MVA

8.35%

31.5MVA

12.5%

MVA

%impedance

Less Than 1MVA

1MVA To 2.5MVA

2.5MVA To 5MVA

5MVA To 7MVA

7MVA To 12MVA

12MVA To 30MVA

10%

More Than 30MVA

12.5%

BUS BAR MATERIALS:

Description Bus Bar and Jumper Material 400 kV Main Bus 114.2 mm dia. Aluminium pipe 400 kV equipment interconnection 114.2 mm dia. Aluminium pipe 400 kV overhead bus & droppers in all bays. Twin ACSR Moose 220 kV Main Bus Quadruple / Twin ACSR Zebra / Twin AAC Tarantulla 220 kV Auxiliary Bus ACSR Zebra 220 kV equipment interconnection Twin ACSR Zebra / Single ACSR Zebra 220 kV overhead bus & droppers in all bays. Twin ACSR Zebra / Single ACSR Zebra 132 kV Main Bus ACSR Zebra 132 kV Auxiliary Bus ACSR Panther 132 kV equipment interconnection ACSR Zebra / ACSR Panther 132 kV overhead bus & droppers in all ba…