Page 601 - Handbook of Electrical Engineering

594 HANDBOOK OF ELECTRICAL ENGINEERING

The proportion of current entering the ground I fe is therefore:-

|I fe |=|Z e I f /(R en + R ep )|
= 0.6826 × 1057.4 = 721.74 amps.

See Case C.3 in Tables H.1c and H.1d.
The corner mesh voltage E m in the centre of the mesh at any corner of the grid is: -

ρI fe K m K i
E m = = 1853.6 volts
L g + 1.15L r
Table H.1c. Data for earth resistance, touch voltage, ground potential rise and corner mesh voltage
for different grid and rod designs
Case Resistivities Area dr hs h Nrod l r N mesh
A
ρ ρ s

A.1 100 1000 36 0.02 0.2 0.5 2 10 3
A.2 100 1000 64 0.02 0.2 0.5 2 10 4
A.3 100 1000 100 0.02 0.2 0.5 4 10 5
A.4 100 1000 144 0.02 0.2 0.5 4 10 6
A.5 100 1000 196 0.02 0.2 0.5 5 10 7
A.6 100 1000 256 0.02 0.2 0.5 5 10 8
B.1 1000 5000 36 0.02 0.2 0.5 2 10 3
B.2 1000 5000 64 0.02 0.2 0.5 2 10 4
B.3 1000 5000 100 0.02 0.2 0.5 4 10 5
B.4 1000 5000 144 0.02 0.2 0.5 4 10 6
B.5 1000 5000 196 0.02 0.2 0.5 5 10 7
B.6 1000 5000 256 0.02 0.2 0.5 5 10 8
C.1 1000 5000 36 0.02 0.2 0.5 2 50 3
C.2 1000 5000 64 0.02 0.2 0.5 2 50 4
C.3 1000 5000 100 0.02 0.2 0.5 4 50 5
C.4 1000 5000 144 0.02 0.2 0.5 4 50 6
C.5 1000 5000 196 0.02 0.2 0.5 5 50 7
C.6 1000 5000 256 0.02 0.2 0.5 5 50 8
D.1 1000 5000 36 0.2 0.2 0.5 2 50 3
D.2 1000 5000 64 0.2 0.2 0.5 2 50 4
D.3 1000 5000 100 0.2 0.2 0.5 4 50 5
D.4 1000 5000 144 0.2 0.2 0.5 4 50 6
D.5 1000 5000 196 0.2 0.2 0.5 5 50 7
D.6 1000 5000 256 0.2 0.2 0.5 5 50 8
E.1 1000 5000 36 0.2 0.2 2.0 2 50 3
E.2 1000 5000 64 0.2 0.2 2.0 2 50 4
E.3 1000 5000 100 0.2 0.2 2.0 4 50 5
E.4 1000 5000 144 0.2 0.2 2.0 4 50 6
E.5 1000 5000 196 0.2 0.2 2.0 5 50 7
E.6 1000 5000 256 0.2 0.2 2.0 5 50 8