Determination of Size of Earth Wire and Earth Plate for Domestic and Motor Installations

Determination of Size of Earth Wire and Earth Plate for Domestic and Motor Installations Points : determination of size of earth wire and earth plate for domestic and motor installations, material required for g.i. pipe earthing, specifications of earth wire and earth plate, pecifications of gi earth plate, earth wire for 50 hp motor, earth wire for 100 hp motor, functions of earthing, what points are to be connected to earth Size of Earth Wire and Earth Plate for Domestic and Motor Installations In case of I w voltage supply, the consumer need not provide his own earthing system, with an independent electrode as the supplier is required to provide and maintain a suitable earthed terminal in an accessible position at or near the point of commencement of supply at the consumer premises.

From sub-main distribution boards copper no 14 SWG wire will be required to run to three-pin socket outlets and connected to their earth sleeve. In case of motor installations consumer is to provide his own earthing system. The size of earth wire and earth plate used will depend upon the rating of the motor for which it is to be used. The conductor used for earthing purpose should not be of cross-section less than that of 14 SWG, and greater than 64.5 mm2 from mechanical consideration. From electrical consideration the copper earth wire should not be of size lesser than current carrying conductor. GI wire may also be used as earth wire provided its conductivity is not lesser than that of copper conductor. The figures regarding size of earth wire for various capacity motors for guidance are given in Table.

Material required for G.I. pipe earthing The list of material with complete specifications for GI pipe earthing is given below:

Specifications of earth wire and earth plate (i) Specifications of Copper Earth Plate 60 cm x 60 cm x 3mm high conductivity copper plate fitted with copper lug, bolt, nut and washer. The finished plate shall have reasonably clean and smooth surface, free from scratches, porosity, black oxide and any other defect. (ii) Specifications of Gi Earth Plate 60 cm x 6 mm GI plate fitted with a GJ lug, bolt, nut and washer. The finished plate shall have reasonably clean and smooth surface free from scratches, porosity and other defect. (iii) Earth Wire For 50 HP Motor No 2 SWG; hard drawn bare copper (HDBC) wire. (iv) Earth Wire For 100 HP Motor No 2 SWG, hard drawn bare copper (HDBC) wire or copper strip of 13 mm x 2.5 mm size. Functions of earthing Earthing may be defined as the process of connecting the non-current carrying parts of electrical apparatus to the general mass of the earth in such a manner that at all times an immediate discharge of electrical energy place without any danger. Two main functions of the earthing are:

1. it is to ensure that no current carrying conductor rises to a potential with respect to general mass of earth than its designed insulation.

2. It is for the safety of the human beings from the electric shocks and for the safety of property for fire. What points are to be connected to earth? The following equipment should be connected to earthing through earth wire as per Indian Electricity Rules.
i) The neutral conductor of 3 phases, 4 wire a.c. electrical system and the middle conductor of two phase, 3 wire system should be earthed by not less than two separate and distinct connections with earth at the generating station and at the sub-station.
ii) Metal frame of generators, motors and other metallic parts of the equipment.
iii) All metal parts of electrical installation such as metal conduits, light fittings, iron clad main switches, iron plad distribution boards, cable sheathes etc.
iv) Earth pin of the three pin lighting and power plug sockets.
v) Steel tower, tubular poles, rail poles, etc. used in overhead transmission line should be earthed.
vi) Stay wires provided for overhead lines.