GAIL (India) Limited

20such that it shall be able to reach the center of the plate. The earthing lead shall be securely bolted theplate with two bolts, nuts, check nuts and washers.3.3. Strip or conductor electrodes:3.3.1 Strip electrode shall not be smaller than 25 x 3 mm. if of copper and 25 x 6 mm. if of galvanized iron andsteel. If round conductors are used as earth electrodes, their cross sectional area shall not be smaller than 3sq.mm if of copper and 6 sq.mn if galvanized iron and steel.4. General:3.3.2 Conductor shall be buried in trenches not less than 0.5 m deep.i) All materials used for connecting the earth lead with electrode shall be of GI in case of GI pipe and GIplate electrodes, and of tinned brass in case of copper plate electrode. The earthing lead shall be securelyconnected at the other end to the main board.ii) The earthing lead from electrode onwards shall be suitably protected against mechanical injury by routingthe earth wire / strip through a suitable size of GI pipe.iii) All medium voltage equipments shall be earthed by two separate and distinct connections with the earth.In the case of high and extra high voltages, the neutral points shall be earthed by not less than twoseparate and distinct connections with the earth, each having its own electrode at the generating station orsubstation.iv) All materials, fittings etc. used in earthing shall conform to Indian standard specifications wherever theyexist. In the case of materials for which Indian standard specifications do not exist, such materials shall beapproved by the Engineer-in-Charge.v) The earth electrode shall be kept free from paint, enamel and grease.vi) It shall be ensured that similar material for respective earth electrodes and earth conductors are used.vii)viii)ix)Earth electrode shall not be installed in proximity to a metal fence.Copper GI strip shall be connected to the respective earth electrodes either by brazing or weldingrespectively. The Copper GI strip shall be jointed only either by brazing or by riveting at the end of overlapping portions The over lap shall not be less than 50 mmEarthing clamps used for supporting earth strips shall be made of such materials so as to avoid bimetallicaction between strip and clamps.5. Testing:The earth resistance of each electrode shall be measured by using a reliable and calibrated earth meggerand the value shall be as per IS/IE rules