SUBSTATION
CONTRACT NO.
TENDER NO.
PROJECT
REVISION
Probe Spacing A
(m)
0.31
0.92
1.52
4.57
6.10
9.15
15.24
21.34
27.44
33.54
39.63
45.73
SUBSTATION EARTHING GRID DESIGN CALCULATION
PMU 275/132/33kV SHAH ALAM SEKSYEN 18 GIS
DATE
Depth of Probe D = A/20 (m)
0.02
0.05
0.08
0.23
0.30
0.46
0.76
1.07
1.37
1.68
1.98
2.29
Measured Resistance R () Apparent Resistance
= 2AR m
29.73
15.33
9.97
3.85
3.15
2.49
1.90
1.56
1.32
1.15
1.01
0.90
56.98
88.15
95.48
110.64
120.71
143.11
182.01
209.21
227.60
242.36
251.55
258.64
Measured Resistance vs Probe Spacing
35.00
30.00
Resistance W
25.00
20.00
15.00
10.00
5.00
0.00
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
50.00
45
50
Probe Spacing (m)
Soil Resistivity vs Probe Spacing
300
250
Resistivity Wm
200
150
100
50
0
0
10
15
20
25
Probe Spacing (m)
30
35
40
0
0
10
15
20
25
Probe Spacing (m)
30
35
40
45
50
SUBSTATION
CONTRACT NO.
TENDER NO.
PROJECT
REVISION
SUBSTATION EARTHING GRID DESIGN CALCULATION
PMU 275/132/33kV SHAH ALAM SEKSYEN 18 GIS
DATE
INPUT PARAMETER
Symmetrical Earth Fault Current, If
31,500.00 A
Duration of Shock Current, ts
0.50 sec
Duration of Fault Current, tf
3.00 sec
Soil Resistivity,
112.20 m
Fence Perimeter
0.00 m
Body Weight
50.00 kg
Decrement Factor (for determining IG), Df
1.00
Fault Current Divisional factor, Sf
0.70
Crushed Rock
Crushed Rock Resistivity, s
Thickness of Crushed Rock, hs
3,000.00 m
0.150 m
Earth Rod
Number of Earth Rod Point
Length of Earth Rod, Lr
165.00
1.80 m
3.00
891.00 m
Quantity of Earth Rod Buried For Each Rod Point
Total Length of Earth Rod Used, LR
Earth Grid Conductor
Cross Section Area of Earth Grid Conductor
Depth of Earth Grid Conductor Burial, h
Grid Reference Depth, ho
Earthing Area, A = Lx x Ly
Earth Grid Section Area, A
Peripheral Length of Earth grid, Lp = 2Lx +2 Ly
300.00 mm2
0.30 m
1.00 m
70.00 m
3.00 m
3.00 m
3,406.67 m
4,900.00 m2
280.00 m
Total Effective Length of Earthing Ssystem Conductor
Length of Earth Rod + Earth Grid, LT
4,297.67 m
Effective Buried Conductor Length, Ls
3,312.35 m
Spacing Between Parallel Conductor, D
Mesh Size of Earthing Grid, Dx x Dy
Total Length of Earth Grid Conductor, LC
70.00 m x
3.00 m x
SUBSTATION
CONTRACT NO.
TENDER NO.
PROJECT
REVISION
SUBSTATION EARTHING GRID DESIGN CALCULATION
PMU 275/132/33kV SHAH ALAM SEKSYEN 18 GIS
DATE
VERIFICATION OF EARTH GRID CONDUCTOR FAULT CURRENT WITHSTAND CAPACITY
SURFACE LAYER DERATING FACTOR, Cs
Surface Layer Derating Factor, Cs
0.78
TOLERABLE STEP VOLTAGE, Estep50
Tolerable Step Voltage For Body Weight 50kg, Estep50
3,330.81 V
TOLERABLE TOUCH VOLTAGE, Etouch50
Tolerable Touch Voltage For Body Weight 50kg, Etouch50
999.23 V
EARTH GRID RESISTANCE, Rg
Earth Grid Resistance, Rg
0.74
SYMMETRICAL GRID CURRENT, Ig
Ig = S f x If
22,050.00 A
MAXIMUM GRID CURRENT, IG
Maximum Grid Current, IG
IG = Df x Ig
22,050.00 A
GROUND POTENTIAL RISE, GPR
Ground Potential Rise, GPR = IG x Rg
16,232.91 V
GPR vs Etouch50
GPR
Etouch50
16,232.91 V
999.23 V
GPR > TOLERABLE TOUCH VOLTAGE
MESH VOLTAGE, EM
na
nb
nc
nd
n = na x nb x nc x nd
24.33
1.00
1.00
1.00
24.33
Ki
Kii
kh
Km
Em
4.25
1.00
1.14
0.35
770.48 V
EM vs Etouch50
EM
Etouch50
770.48 V
999.23 V
MESH VOLTAGE < TOLERABLE TOUCH
VOLTAGE, DESIGN OK
STEP VOLTAGE, Es
Es
2,324.48 V
Es vs Estep50
Es
Estep50
2,324.48 V
3,330.81 V
STEP VOLTAGE < TOLERABLE STEP
VOLTAGE, DESIGN OK
SUBSTATION EARTHING GRID DESIGN CALCULATION
SUBSTATION
PMU 275/132/33kV SHAH ALAM SEKSYEN 18 GIS
CONTRACT NO.
TENDER NO.
PROJECT
REVISION
DATE
Legend
s
A
Cs
d
Dm
Df
Em
Es
Estep50
Etouch50
h
hs
IG
Ig
kh
Ki
Kii
Km
Ks
n
Soil resistivity.
Surface layer resistivity.
Total area enclosed by earth grid.
Surface layer derating factor.
Diameter of grid conductor.
Maximum distance between any two points on the grid.
Decrement factor for determining IG.
Mesh voltage at the centre of the corner mesh for the simplified method.
Step voltage between a point above the outer corner of the grid and a point 1m diagonally outside the
grid for the simplified method.
Tolerable step voltage for human with 50kg body weight.
Tolerable touch voltage for human with 50kg body weight.
Depth of earth grid conductors.
Surface layer thickness.
Maximum grid gurrent that flows between earth grid and surrounding earth.
Symmetrical grid current.
Corrective weighting factor that emphasizes the effects of grid depth, simplified method.
Correction factor for grid geometry, simplified method.
Corrective weighting factor that adjusts for the effects of inner conductor on the corner mesh,
simplified method.
Spacing factor for mesh voltage, simplified method.
Spacing factor for step voltage, simplified method.
Geomatric factor composed of factors na, nb, nc and nd.
SURFACE LAYER DERATING FACTOR, Cs
Equation 27
TOLERABLE STEP VOLTAGE, Estep50
Equation 29
TOLERABLE TOUCH VOLTAGE, Etouch50
Equation 32
EARTH GRID RESISTANCE, Rg
Equation 52
SYMMETRICAL GRID CURRENT, Ig
Equation 65
MAXIMUM GRID CURRENT, IG
Equation 64
GROUND POTENTIAL RISE, GPR
Assumption Ig = IG
MESH VOLTAGE, EM
Equation 81
Equation 83
Equation 82
Equation 85
Equation 86
Equation 87
Equation 88
Equation 84
Equation 80 & Equation 91
STEP VOLTAGE, Es
Equation 89
Equation 93
Equation 94
Equation 92
EARTHING GRID DESIGN CALCULATION
ALAM SEKSYEN 18 GIS
nt above the outer corner of the grid and a point 1m diagonally outside the
d.
that emphasizes the effects of grid depth, simplified method.
that adjusts for the effects of inner conductor on the corner mesh,
