Earthing and Grounding
Connecting equipment and system neutrals to earth for safety and protection operation.
System earthing connects the neutral of transformers/generators to earth; equipment earthing connects exposed metal parts, so a fault causes enough current to trip the protection instead of making the enclosure live.
Earthing systems (IEC): TN-S, TN-C-S, TT, IT. Earth electrodes: pipe, plate or rod earthing, with chemical/maintenance-free electrodes common. Indian practice is guided by IS 3043 and the CEA safety regulations.
The earth resistance must be low enough for protection to operate — commonly targeted values range from about 1 Ω (substations) to a few ohms for installations. Equipotential bonding of metal pipes and structures reduces touch voltages. Lightning protection (IS/IEC 62305) is a related but separate system.
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