Earth electrode shall be of copper-jacketed steel core rods with 16mm diameter and supplied in 1500mm length and shall have provision for
screw coupling with another standard length. The copper jacket of 99.9 % purity electrolytic copper shall be of minimum radial thickness 0.25mm and shall be molecularly bonded to the steel core to ensure that the copper jacket and steel core are not separable. Each earth electrodes shall be driven 3000mm in depth.
Where the desired earth resistance value cannot be achieved after the first earth electrode have been driven, sufficient number of earth electrodes in parallel shall be installed outside the resistance area until required value is reached. Mutual separation between two earth electrodes shall be more than the driven depth of the earth electrode but less than twice the driven depth. Interconnection between different earth electrodes shall be by means of 25mm x 3mm annealed copper tape.
The connection of the annealed copper tape to the earth electrode shall be soundly made by the use of plumbed joints, either by brazing using zinc-free material with a melting point of at least 600 0C or by exothermic welding or by cold pressure welding.
Each earth electrode shall be provided with heavy-duty type inspection chamber with removable cover. The compressive strength of the inspection chamber and cover shall be minimum 6 N/mm2. Lifting hook shall be provided in the cover.
Each earth electrode shall be identified by permanent label legibly marked with words “Lightning Protection Earth – Do Not Remove” permanently
fixed at the point of connection of every down conductor to an earth termination and at every earth electrodes.