Continuity: Ensure that complete earthing system is electrically continuous and mechanically secure. Locations of main earth bars in substations, electrical rooms, mechanical rooms, hub (Technical) rooms, etc., to be clearly identified by 100mm X 100mm white traffolyte labels, with red lettering, to Engineer's approval.
Main earth bars to be provided in all electrical rooms, hub (Technical) rooms and plant rooms, located so as to be easily accessible and protected by a 2mm thick aluminium plate against inadvertent damage.
Earth Rods: While siting earth rods, ensure that resistance areas associated with individual rods do not overlap. Earth rods are to be located at a distance greater than 600 mm from foundations of buildings. Where rock is encountered, a hole of sufficient size is to be drilled before lowering the rod. Conductive filler such as Marconite or Bentonite or equal filler that will not corrode is to be provided around the rod.
The rods shall be installed by driving into the ground with a power hammer of suitable design to ensure the minimum of distortion to the rod. Where it is not possible to drive rods to the full depth required due to the presence of a stratum of rock, then holes shall be drilled or blasted in the rock. The holes shall be filled with bentonite or other approved material prior to inserting the rod.
Spacing between earth rods shall not be less than that stipulated by the IEC. Buried earthing conductors are to be laid at a depth not less than 0.8 m from ground surface.
Earthing conductors are to follow shortest path between earth rods and main earthing terminals or bars, and are to run in PVC conduit (duct) fastened to building structure by approved supports and extending 0.2 m above level, and are to be protected against mechanical damage and corrosion.
Protective Conductors: Separate protective conductors, which are not part of a cable, are to be fixed on same support or drawn into same conduit as circuit conductors.
Protective Bonding: Remove any non-conductive paint, enamel or similar coating at threads, contact points and surfaces and ensure that bonding is made by fittings designed to make secure bonds. The diameter of any holes drilled in strip conductors shall not be greater than half the width of the strip.
Connections to electrical equipment shall be detachable and made at the earthing studs or bolts provided on the equipment by the manufacturer. When an earthing point is not provided the point and method of connection shall be agreed with the Engineer.