Methods of Earthing System

Methods of Earthing System Points : methods of earthing system, earthing through a water main, pipe earthing, plate earthing Three are three methods of earthing
1. Earthing Through a Water Main
2. Pipe Earthing
3. Plate Earthing 1. Earthing Through a Water Main Before making an earthing connection to the water main, it must be ascertained that throughout G.I. pipes have been used, otherwise if the cement concrete pipes have been used, the earthing will not be effective. When making an earthing connection, care must be taken to limit the contact resistance to the minimum. For that purpose properly designed earthing clamp should be used. The stranded copper lead is fanned out and is soldered to make it solid. Then the lead strip is bent round the pipe so that it may be seated properly over the pipe. The surface ofthe pipe is cleaned properly, and all traces or grease are removed and then over it is placed the clamp. In between the clamp and pipe is inserted the lead and is tightened with the screws. This method is however not popular as water means are of concrete or cement. 2. Pipe Earthing If the water-pipe cannot be used as an earth, a galvanized iron pipe of approved length and diameter can be sued. The size of the pipe depends upon (a) the current to be, carried (b) the type of soil. According to I.S.I. Standard No. 732-1963 the galvanized iron pipe shall not be less than 38.1 mm. Diameter and 2m long for ordinary soil hut if the soil is dry and rocky, the length of the pipe should be increased to 2.75m.

The pipe is placed upright as shown, and must be placed in a permanently wet ground. The depth at which the pipe should be buried depend on the condition of the ground moisture. According to Indian Standard, the pipe should be placed at a depth of 4.75m; it can be less if the soil provides sufficient moisture earlier. The pipe at the bottom should be surrounded by broken pieces of coke or charcoal for a distance of about 15cm. Around the pipe. The coke increases the effective areas of the earth practically to the outside of the coke bed. Impregnating the coke with salt decreases the earth resistance. Generally alternate layers of salt and coke are used for best results as represented, in summer season the moisture in the soil will decrease to a large extent which will increase the Earth resistance, so in order to have an effective earth, whenever needed, 3 to 4 buckets of water should be put into the funnel connected to the main G.I. pipe through 19mm. Dia. Pipe.

The earth lead used must be G.I. wire or G.I. strip (not of copper) of water should be put into the funnel connected to the main G.I. pipe through 19mm. Dia. Pipe. The earth lead used must be G.I. wire or G.1. strip (not of copper) of sufficient cross-sectional area to carry fault current safely. (It should not be less than electrical equivalent of copper conductor of 12.97 sq. mm (8 SWG) cross-sectional area. The earth wire from the G.I. pipe of 19mm dia. Should be carried in a G.I. pipe of dia. 12.7 mm. At a depth of about 60 cm. Below the ground. Further when the earth wire is carried over from one machine to the other, it should be well protected from mechanical injury, be carrying the earth wire in a recessed portion. 3. Plate Earthing The earth connection can again be provided with the help of a copper plate or G.I. pipe. When 0.1 plate is used it should not be of less than 60cm x 60cm. X 6.35mm while for copper plate these dimensions may be 60cm. X 60cm. X 3.18 mm. However, the use of the copper plate in these days, is limited.