GAIL (India) Limited
GAIL (India) Limited GAIL (India) Limited
19CHAPTER 4EARTHING1. SCOPE:This specification is intended to cover the requirements of supply, installation, testing and commissioningofa) Pipe earthingb) Plate earthingc) Strip earthing2. STANDARDS:Earthing installations shall conform to the Indian Electricity Rules - 1956. as amended from time to timeand IS 3043-1989 “code of practice for earthling” with latest amendments.3. Earth electrode arrangement:3.1 Pipe electrode-:3.1.1 Electrode shall be made of CI pipe having a clean surface and not covered with paint. Enamel or poorlyconducting material. Galvanized pipe shall not be smaller than 100 mm ID. Earthing with pipe electrodeshall be done as per the details indicated in IS: 3043/87.3.1.2 Electrode shall be made of GI pipe having 40mm ID with ‘C’ class GI pipe.3.1.3 Electrodes shall be embeded below permanent moisture level3.1.4 The length of pipe electrodes shall not be less than 2.5 m. if rock is encountered, pipes shall be driven to adepth of not less than 1.5 m with 2 nos. of pipes of electrodes with a gap of 2mts. and inter connected.Pipe shall be in one piece and deeply driven.3.1.5 To reduce the depth of burial of an electrode without increasing the resistance, a number of rods or pipesmay have to be connected together in parallel. The distance between two electrodes in such a case shallnot be less than twice the length of the electrode. The earthing lead shall be connected by means of a-through bolt, nuts and washers and cable socket.3.2 Plate electrode:For plate electrodes, minimum dimensions of the electrode shall be as under.3.2.1 GI plate electrode 600 x600 x 6 mm thick3.2.2 Copper plate electrode 600 x 600 x 3 mm thick3.2.3 The electrode shall be buried in ground, with its face vertical and top not less than 2.5 M from the surfaceof the ground.3.2.4 Earthing using plate electrode shall be done as per details indicated in drawing.3.2.5 Plate electrodes shall have galvanized iron water pipe, buried vertically and adjacent to the electrode. Oneend of pipe shall be atleast 5 cm above the surface of the ground and need not be more than 10 cm. Theinternal diameter of the pipe shall be at least 19 mm. The length of pipe under the earth’s surface shall be
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
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19CHAPTER 4EARTHING1. SCOPE:This specification is intended to cover the requirements of supply, installation, testing and commissioningofa) Pipe earthingb) Plate earthingc) Strip earthing2. STANDARDS:Earthing installations shall conform to the <strong>India</strong>n Electricity Rules - 1956. as amended from time to timeand IS 3043-1989 “code of practice for earthling” with latest amendments.3. Earth electrode arrangement:3.1 Pipe electrode-:3.1.1 Electrode shall be made of CI pipe having a clean surface and not covered with paint. Enamel or poorlyconducting material. Galvanized pipe shall not be smaller than 100 mm ID. Earthing with pipe electrodeshall be done as per the details indicated in IS: 3043/87.3.1.2 Electrode shall be made of GI pipe having 40mm ID with ‘C’ class GI pipe.3.1.3 Electrodes shall be embeded below permanent moisture level3.1.4 The length of pipe electrodes shall not be less than 2.5 m. if rock is encountered, pipes shall be driven to adepth of not less than 1.5 m with 2 nos. of pipes of electrodes with a gap of 2mts. and inter connected.Pipe shall be in one piece and deeply driven.3.1.5 To reduce the depth of burial of an electrode without increasing the resistance, a number of rods or pipesmay have to be connected together in parallel. The distance between two electrodes in such a case shallnot be less than twice the length of the electrode. The earthing lead shall be connected by means of a-through bolt, nuts and washers and cable socket.3.2 Plate electrode:For plate electrodes, minimum dimensions of the electrode shall be as under.3.2.1 GI plate electrode 600 x600 x 6 mm thick3.2.2 Copper plate electrode 600 x 600 x 3 mm thick3.2.3 The electrode shall be buried in ground, with its face vertical and top not less than 2.5 M from the surfaceof the ground.3.2.4 Earthing using plate electrode shall be done as per details indicated in drawing.3.2.5 Plate electrodes shall have galvanized iron water pipe, buried vertically and adjacent to the electrode. Oneend of pipe shall be atleast 5 cm above the surface of the ground and need not be more than 10 cm. Theinternal diameter of the pipe shall be at least 19 mm. The length of pipe under the earth’s surface shall be
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