Earthing Coil and Knob
The earthing knob is used for supporting the neutral-cum-earth wire used for earthing of metal elements of supporting structures of low-tension lines, i.e., 400/230 V lines. The knob is commonly made of cast iron 52x42 mm and its electrical resistance is not to exceed 200 mega ohms. Therefore, the breaking strength at the neck of the knob is not to be less than 11,500 kg while force is applied.
Two types of earthing arrangements are used. One is along with GI pipe and the other is within GI wire. In that case of GI pipe earthing, 40 mm dia and 2500 mm long pipe is used for earthing of supports and fittings. GI wire is used for earthing of lines. Commonly 8 SWG wire along with 115 turns, 50 mm dia and 1500 mm length is used.