Earth Resistance Value

Earth Resistance Value Points : earth resistance value, what are the factors on which earth resistance value depends? how earth resistance can be reduced? Earth resistance value depends upon:
a) Condition of Soil.
b) Moisture of the soil
c) Temperature of the soil.
d) Depth of the electrode at which it is embedded.
e) Size and spacing of earth electrodes.
f) Metal of earth plate and earth wire.

The value of earth resistance can be reduce by increasing moisture of the, soil. Thus fresh salt water is poured in earth pit. The value of earth resistance normally should not be more than 1Ω. Some of the maximum permissible values of earth resistance for satisfactory results are:

1. Large power stations = 0.5 ohms
2. Major power stations = 1.0 ohms
3. Small sub-stations 2.0 ohms
4. In all other cases 0.8 ohms