GAIL (India) Limited
GAIL (India) Limited GAIL (India) Limited
25CHAPTER 6LIGHTNING PROTECTION1. Scope:This specification is intended to cover the requirements of supply, installation and testing of lightningprotection system at plaices specified by the department.2. Standards:The lightning protection system shall conform to the 1S: 2309/1989 and National Electrical code.3. Terminology:i) Air termination (lightning conductor) or Air termination network. Those pans of lightning protectionsystem that are intended to collect the lightning discharges from the atmosphere.ii) Bonds: Electrical connection between the lightning protection system and other metal work, and betweenvarious portions of the latter.iii) Down conductors: Conductors, which connect the air terminations with the earth terminations.iv) Earth terminations or earth terminations net work: Those parts of the lightning protection system whichare intended to distribute the lightning discharges into the general mass of the earth. All parts below thetesting point in a down conductor are included in this term.v) Earth electrodes: A metal plate, pipe or other conductor or an array of conductors electrically connected tothe general mass of the earth. These include those portions of the earth terminations that make directelectrical contact with the earth.vi) Lightning protection system: The whole system interconnected conductors used to protect a structure fromthe effects of lightning.vii) Side flash: A spark occurring between nearby metallic objects or between such objects and the lightningprotection system to earth.viii) Testing points: Joints in down conductors or in bonds or in earth conductors connecting earth electrodes,so designed and situated as to enable resistance measurements to be made.4. Materials to be used:Materials to be used in the lightning protection system shall be reliably resistant to corrosion oradequately protected against corrosion. The materials to be used are.i) Copper: Solid, or flat copper strips or stranded copper wire of 98 per cent conductivitywhen annealed, shall be used.ii) Galvanized: It shall be protected against corrosion in zinc coating.5. Lightning protection system:5.1 Air terminations:The lightning protection system comprises of the following major components.i. Air terminationsii. Down conductorsiii. Joints and bondsiv. Testing pointsv. Earth terminationsvi. Earth electrodesvii. FastenersIt shall consist of a vertical conductor on a tall structure, a single horizontal conductor for a small buildingand system of horizontal and vertical conductors for the protection of bigger buildings.
26A vertical air termination shall project at least 30 cm above the building, which it is fixed.All horizontal air terminations shall be interconnected such that no part of the roof is more than 5 m awayfrom the nearest horizontal conductor. For a flat roof, horizontal air terminations shall be fixed along theouter perimeter of the roof.Horizontal air termination shall be fixed along contours of the roof of the buildings in such a way as tojoin each air termination to the rest and shall they form a closed network.All metallic finials, Chimneys, ducts, vent pipes, railings, gutters etc. on or above the main surface of theroof of the structure shall be bonded to the air terminations network. A typical fixing detail of vertical airtermination on flat roof building is shown in drawing.All terminals shall be firmly fixed to the building in order to avoid overturning.5.2 Down conductors:5.2.1 Down conductors shall be distributed around the outside walls of the structure and run along the cornersand other projections, considering the location of air terminations and earth terminations. Lift shafts shallnot be used for fixing down conductors.5.2.2 The down conductors shall be routed in the most direct path possible between the air termination avoidingsharp bends, up turns and links. Joints shall be avoided in down conductors. Metal pipes shall not be usedas protection for the conductors.5.2.3 In buildings of cantilever construction, down conductors shall be taken straight down to ground by routingthrough a nonmetallic, non-combustible internal duct. Any covered recess not smaller than 75 x 1 5 mmor any vertical service duct running the full height of the building shall also be used for this purpose,provided it does not contain an unarmored or non-metal sheathed cable.The routing of the down conductor shall be such that its accessibility for inspection, testing andmaintenance is ensured.5.2.4 It shall be ensured that the same material is used for both air termination and down conductor. Forexample if GI strip is used for air termination, the down conductor shall also be of GI strip.5.2.5 The shapes and minimum sizes of conductors for use above ground and below ground given in IS 2309 -1989 is reproduced below for ready reference.Sl. No Materials and Shape Minimum size(i)Above ground:a) Round copper wire 6 min diameterb) Standard copper wire 50 mm sq.c) Copper strip 20 x 3 mmd) Round galvanised iron wire 8 mm diametere) Galvanised Irron Strip 20 x 3 mmf) Round aluminium wire 9 mm diameterg) Aluminium strip 25 x 3.15 mm(ii)Below ground:a) Round copper wire 8 mm diameterb) Copper strip 32 x 6 mmc) Round galvanised iron wire 10mm diad) Galvanised iron strip 32 x 6 mm
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26A vertical air termination shall project at least 30 cm above the building, which it is fixed.All horizontal air terminations shall be interconnected such that no part of the roof is more than 5 m awayfrom the nearest horizontal conductor. For a flat roof, horizontal air terminations shall be fixed along theouter perimeter of the roof.Horizontal air termination shall be fixed along contours of the roof of the buildings in such a way as tojoin each air termination to the rest and shall they form a closed network.All metallic finials, Chimneys, ducts, vent pipes, railings, gutters etc. on or above the main surface of theroof of the structure shall be bonded to the air terminations network. A typical fixing detail of vertical airtermination on flat roof building is shown in drawing.All terminals shall be firmly fixed to the building in order to avoid overturning.5.2 Down conductors:5.2.1 Down conductors shall be distributed around the outside walls of the structure and run along the cornersand other projections, considering the location of air terminations and earth terminations. Lift shafts shallnot be used for fixing down conductors.5.2.2 The down conductors shall be routed in the most direct path possible between the air termination avoidingsharp bends, up turns and links. Joints shall be avoided in down conductors. Metal pipes shall not be usedas protection for the conductors.5.2.3 In buildings of cantilever construction, down conductors shall be taken straight down to ground by routingthrough a nonmetallic, non-combustible internal duct. Any covered recess not smaller than 75 x 1 5 mmor any vertical service duct running the full height of the building shall also be used for this purpose,provided it does not contain an unarmored or non-metal sheathed cable.The routing of the down conductor shall be such that its accessibility for inspection, testing andmaintenance is ensured.5.2.4 It shall be ensured that the same material is used for both air termination and down conductor. Forexample if GI strip is used for air termination, the down conductor shall also be of GI strip.5.2.5 The shapes and minimum sizes of conductors for use above ground and below ground given in IS 2309 -1989 is reproduced below for ready reference.Sl. No Materials and Shape Minimum size(i)Above ground:a) Round copper wire 6 min diameterb) Standard copper wire 50 mm sq.c) Copper strip 20 x 3 mmd) Round galvanised iron wire 8 mm diametere) Galvanised Irron Strip 20 x 3 mmf) Round aluminium wire 9 mm diameterg) Aluminium strip 25 x 3.15 mm(ii)Below ground:a) Round copper wire 8 mm diameterb) Copper strip 32 x 6 mmc) Round galvanised iron wire 10mm diad) Galvanised iron strip 32 x 6 mm
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