(Seminar on Earthing Systems - 21-22 May, 2008 pp. 130-132)
Earthing is the system of connection to the general mass of earth. Earthing systems are usually installed for one or more of the following purposes:
Power system is earthed primarily to preserve the security of the system. This is achieved by ensuring that the voltage on each conductor is restricted and is consistent with the level of insulation.
Power system is earthed to obtain safety by ensuring, efficient and fast operation of protective gear in the case of earth faults. Such protective operation involves isolation of faulty circuit, by either a circuit breaker or a fuse.
Distribution system is earthed to enable implementation of protective earthing schemes like TN-S, TN-C Systems etc.
To conduct lightning discharge current to earth
To obtain equipotential bonding and equipment protection
In Tele-communication circuits to obtain an earth path for signalling, stabilize the potential of equipment with respect to earth, to screen the conductors to reduce electrical interference etc.
To obtain low noise earth in Data Processing Installations
Most importantly to protect human life from electric shock hazards.
