You would have noticed that electrical equipment commonly used viz.
Heater, Iron, Geyser, Cooler, Friz etc., have three wires in their main lead, which are generally of red, black and green colours. The red colour wire is connected with the Phase and the black one with the Neutral. The third green wire is for the earthing, which is connected to the earthing pin, which has its connection with the body of the equipment. This way the body earth is provided. This body earth is done for the security point of view, because of some times in the body of the equipment, the phase supply appears, which causes shocks. It is a must to earth the equipment to get the human being safe from the electric shocks.
To prepare earth, a pit is digged up to the damp level of the earth and the earth wire is brought up to this depth. Some quantity of coal and salt is also thrown at this place to keep this portion damp. The earthing is a must at least in those electrical
equipments in which the consumption of current is more. Because in such equipments the chances of Phase leakage are more. Three pin plugs are used with such equipments. Even the sockets used for such equipments are of big sizes as the small size sockets generally burn or melt because of the produced heat during the excessive flow of current. No doubt the best earthing arrangements are done in the power houses, and every second or the third pole is earthed still the earthing in the houses and the factories is needed to avoid accidents and for security purposes. Also sometimes some people use the water pipes for the earthing purpose, but this is the totally insecure arrangement, as the very possible phase leakage may cause serious mishaps, the chances of electric shocks the entire water supply network in the house is also possible.
Method of Earthing
For preparing good earthing, first of all dig a pit of 2 to 2.5 Meters deep. Its width should be such that a metal plate of 60cm x 60 cm x 6 mm size may be kept in side easily. Such plates are made of Copper or Galvanized iron. To this plate, the Galvanized wire meant for earthing is tightly fastened or welded. Before putting this plate inside a thick layer of Coal and Salt is layed down. Then after putting the plate again a layer of Coal and Salt is laied. Then good quantity of water is sprinkled over it and the pit is covered perfectly. The wire coming out of the pit is the perfect earth wire. The metal of the wire and the plate should be the same. Generally the diameter of the wire for domestic earthing should be 14 guage. It is better to use a pipe to upbring this wire out of the pit to enable to pour some water occasionally into the pit, and also the gases of inside the pit may exhaust.
The water through the earth pipe is poured to keep the Coal and Salt mixture damp, to get the best earthing results. The diameter of the pipe is generally in between 14 mm to 30 mm. For proper earthing 10 Kg. to 25 Kg. Salt and 10 Kg. to 15 Kg. Wood Coal is required.
For three phase supply, double earthing is provided. For this earthing,
either two different pits are dragged, or two different earthing plates are kept inside the pit at a bit distance.