GAIL (India) Limited

275.2.6 During installation of air terminations and down conductors, the following items shall be taken intoconsideration.i) The mechanical forces produced in case of lightning stroke.ii)External local heating.iii)The Consultantural or aesthetic beauty of the building.iv)Services entering the structure above and below groundv) Radio and television receiver aerials.vi)Flag masts and roof level plant rooms.5.3 Joints and bonds:5.3.1 Joints: It shall he ensured (hat the joints are avoided in the lightning protection system as far as possible.In case joints becomes necessary, the number of joints shall be kept as minimum as possible and theyshall be mechanically and electrically effective. The joints shall be bolted, crimped, riveted or welded. Incase of over lapping joints the length of the overlap shall not be less than 20mm. in the down conductorbelow ground level, there shall not be any joint.5.3.2 Bonds: The bond to the lightning protection system shall have a cross sectional area not less than thatemployed for the main conductors. All bonds shall be suitably projected against corrosion and shall be asshort as possible.5.4 Testing points:Each down conductor shall be provided with a testing point at a height of 1.5M from the ground level. Itshall be ensured that there is no connection other than the direct connection to the earth electrode is madebelow a testing point. The details of the test links are shown in the drawing.5.5 Earth terminations:Each down conductor shall have an independent earth termination and have provision for isolation fortesting purpose. Water pipe system shall not be bonded to the earth termination system. However ifadequate clearance between the two cannot be obtained, they may be effectively bonded and the bondsshall be capable of isolation and testing. The gas pipes however shall in no case be bonded to the earthtermination.5.6 Earth electrodes:5.6.1 Earth electrodes shall consist of pipe, strips or plates. Metal sheaths of cables shall not be used as earthelectrodes. The earth electrode shall be constructed as per IS: 30435.6.2 When pipes are used they shall be driven into the ground as close as practicable but outside thecircumference of the structure.5.6.3 When strips are used, they shall be buried at a depth not less than 0.5 m deep. The strips shall be laidradially in two or more directions from the point of connection to a down conductor. If this is not possiblethey shall be laid in one direction. If the space restriction -requires the strips to be laid in parallel or ongrid formation, the distance between two strips shall not be less than 2m.5.6.4 When plate electrodes are used they shall be buried in the ground so that the top edge of the plate is at adepth not less than 2.5m from the surface of the ground. If two plate electrodes are to be used in parallel,the distance between two shall not be less than 8m.5.7 FastnersThe conductors used for lightning protection shall be securely attached to the building or other object tobe protected through fasteners made of galvanized steel. The fasteners shall be substantial in constructionnot subjected to breakage and protected against corrosion. Guidelines given in page 24 IS 2309-1969 shallbe referred.