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Electrical Clearance in Substation
APRIL 6, 2011
57 COMMENTS (HTTPS://ELECTRICALNOTES.WORDPRESS.COM/2011/04/06/ELECTRICAL-CLEARANCEIN-SUBSTATION/#COMMENTS)
Minimum Clearance in Substation:
Voltage
Highest
Voltage
Lighting
Impulse
Level
(Kvp)
Switching
Impulse
Level
(Kvp)
Minimum
Clearance
PhaseEarth
PhasePhase
Safety
Clearance(Mt)
Ground
Clearance(Mt)
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
950
1.900
1.900
4.300
5.500
1050
1.900
1.900
4.300
5.500
3.400
4.200
6.400
8.000
220KV
400KV
245KV
420KV
1425
1050(P-E)
Electrical Clearance in Substation:
Voltage
Height of
I Bay
From
Ground
(Mt)
Height
of II
Bay
From
Ground
(Mt)
Bay Width
(Mt)
PhasePhase
(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
Low
High
Take of
Elevation
(Meter)
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11KV/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 Discfor
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
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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
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
A
5.2
8.5
28.55
B
5.25
10.5
29.08
C
6.7
12.6
31.68
132KV
220KV
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
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400/220KV
315MVA
3 directional 3 directional Differential,
O/L relays
O/L relays
Over
(with dir.
(with dir.
flux,Buchholz,
High set) +1 High set)+1
OLTC PRV, OT,
directional
directional
WT and
E/L relays.
E/L relays.
overload (alarm)
Restricted
Restricted
relay
E/F relay + 3 E/F relay
Directional
O/L relays
for action
The bo�om 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
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