Correct Answer - Option 2 : 25 mm × 1.6 mm
Strip earthing: This type of earthing is used at places which have rocky earth bed.
In this system of earthing, the strip electrode of the cross-sectional area not less than 25 mm × 1.6 mm if copper and 25 mm × 4 mm if GI or steel.
It buried in horizontal trenches of a minimum depth of 0.5 m.
Rod earthing: This system of earthing is suitable for areas that are sandy in character.
This system of earthing is very cheap as no excavation work is involved.
Plate earthing: It is used for larger stations and transmission lines, where the fault current, likely to be high.
Pipe earthing: It is used for ordinary soil or dry and rocky soil.
The size of the pipe depends upon the current to be carried and the type of soil.
Usually, the pipe used for this purpose is of diameter 38 mm and 2.5 meters in length for ordinary soil or of greater length in case of dry and rocky soil.
