Electrical Clearance in Substation Minimum Clearance in Substation:

Voltage Highest Voltage

Lighting Impulse Level (Kvp)

Switching Impulse Level (Kvp)

Minimum Clearance

Safety Clearance(Mt)

Ground Clearance(Mt)

Phase-Earth

Phase-Phase

11KV 12KV 70 0.178 0.229 2.600 3.700 33KV 36KV 170 0.320 0.320 2.800 3.700 132KV 145KV 550 1.100 1.100 3.700 4.600

650 1.100 1.100 2.700 4.600 220KV 245KV 950 1.900 1.900 4.300 5.500

1050 1.900 1.900 4.300 5.500 400KV 420KV 1425 1050(P-E) 3.400 4.200 6.400 8.000

Electrical Clearance in Substation:

Voltage Height of I Bay From Ground (Mt)

Height of II Bay From Ground (Mt)

Bay Width (Mt)

Phase-Phase (Mt)

BetweenEquipment Earth Wire From Ground

132KV (Single)

8.0 - 11.0 3.0 3.0 10.5

220KV (Single)

12.5 - 18 4.5 4.5 15.5

220KV (Double)

18.5 25 25 4.5 4.5 28.5

400KV 15.6 22 22.0 7.0 >6.0 30.0

Standard Bay Widths in Meters:

Voltage Bay Width (Meter) 11KV 4.7 Meter 33KV 4.7 Meter 66KV 7.6 Meter 132KV 12.2 Meter 220KV 17 Meter 400KV 27 Meter

Standard Bus and Equipment Elevation

Voltage Equipment live Terminal Elevation (Meter)

Main Bus Take of Elevation (Meter) Low High

11 KV/33KV 2.8To 4 5.5 To6.5 9 6.5To8.5 66KV 2.8To 4 6To8 9To 10.5 9.5 132KV 3.7To5 8To9.5 13.5To14.5 12To12.5 220KV 4.9To5.5 9To13 18.5 15To18.5 400KV 8.0 15.5 - 23

Phase spacing for strung Bus:

Voltage Clearance 11KV 1300 mm 33KV 1300 mm 66KV 2200 mm

132KV 3000 mm 220KV 4500 mm 400KV 7000 mm

Minimum Clearance of Live Parts from Ground:

Voltage Minimum Clearance to Ground (Mt)

Section Clearance (Mt)

11KV 3.700 2.600 33KV 3.700 2.800 66KV 4.600 3.000 132KV 4.600 3.500 220KV 5.500 4.300 400KV 8.000 7.000

Insulator String:

Voltage No of Suspension String

Length (mm)

No of Disc for Tension String

Length in (mm)

66KV 5 965 6 1070 132KV 9 1255 10 1820 220KV 14 1915 15 2915 400KV 23 3850 2 X 23 5450

Nominal Span:

Voltage Normal Span (Meter) 66KV 240-250-275 132KV 315-325-335 220KV 315-325-335 400KV 315-325-335

Minimum Ground Clearance:

Voltage Ground (Meter) 66KV 5.5 132KV 6.1 220KV 7.0 400KV 8.0 800KV 12.4

Indoor Substation Minimum Clearances

Distance Descriptions 0.9 Meter Horizontally between any item of equipment and

thesubstation wall 0.6 Meter Horizontally between any Two items of equipment 1.2 Meter Horizontally in front of any HV switchgear

Clearance of Conductor on Tower

Voltage Tower Type Vertical Space (Mt) Horizontal Space(Mt) Total Height From Ground(Mt) 66KV

A 1.03 4.0 15.91 B 1.03 4.27 15.42 C 1.22 4.88 16.24

132KV A 7.140 2.17 23.14

B 4.2 6.29 22.06 C 4.2 7.15 22.68 D 4.2 8.8 24.06

220KV

A 5.2 8.5 28.55 B 5.25 10.5 29.08 C 6.7 12.6 31.68 D

NORMS OF PROTECTION FOR EHV CLASS POWER TRANSFORMERS

Voltage ratio & capacity HV Side LV Side Common relays 132/33/11KV up to 8 MVA 3 O/L relays +

1 E/L relay 2 O/L relays + 1 E/L relay

Buchholz, OLTC Buchholz, OT, WT

132/33/11KV above 8 MVA and below 31.5 MVA

3 O/L relays + 1 dir. E/L relay

3 O/L relays + 1 E/L relay

Differential, Buchholz, OLTC Buchholz, OT, WT

132/33KV, 31.5 MVA & above

3 O/L relays + 1 dir. E/L relay

3 O/L relays + 1 E/L relay

Differential, Over flux,Buchholz, OLTC PRV, OT, WT

220/33 KV, 31.5MVA & 50MVA 220/132KV, 100 MVA

3 O/L relays + 1 dir. E/L relay

3 O/L relays + 1 dir. relay

Differential, Over flux,Buchholz, OLTC PRV, OT, WT

400/220KV 315MVA 3 directional O/L relays (with dir. High set) +1 directional E/L relays. Restricted E/F relay + 3 Directional O/L relays for action

3 directional O/L relays (with dir. High set)+1 directional E/L relays. Restricted E/F relay

Differential, Over flux,Buchholz, OLTC PRV, OT, WT and overload (alarm) relay

The bottom most portion of any insulator or bushing in service should be at a minimum height of 2500 mm above ground level.

Location of L.A (From T.C Bushing):

Voltage BIL KV Peak Distance (Mt) 11KV 75 12 33KV 200 15 66KV 325 24 132KV 550 35 220KV 900 To 1050 Close To T.C 400KV 1425 To 1550