SOLUTION

The resistance of the earth depends on the following factors.

• Condition of soil.
• The moisture content of the soil.
• The temperature of the soil.
• Depth of electrode at which it is embedded.
• Size, material, and spacing of earth electrode.
• Quality and quantity of coal and salt in the earth pit.

Perfectly dry Earth is very nearly an insulator and it is quite clear that the current flow is due to the moisture contained in the soil; meaning that the earth resistance is electrolytic in character. The specific resistance of any soil, therefore, depends on the extent of moisture and the manner it is held.

Soil resistivity is one of the most important factors affecting the performance of the earthing system because the value of the earth resistance is directly proportional to the resistivity of the medium in which the earth electrodes are installed. At locations where multilayer soil exists at rather shallow depths, the average or apparent resistivity depends on the layer structure, the soil resistivity, and the depth of each layer.