Working of Ground Wires
Direct lightning strokes on transmission lines represent the major source of the failed power system. The objective of the good line design. Therefore, should be to reduce the number of interruptions due to lightning. This objective demands a two-point procedure-first, the incidence of direct strokes to the system should be minimum and secondly, the amplitude and steepness of the overvoltage arising out of the few strokes that will hit the lines should be kept to a minimum. On both the counts, ground wires are found to be suitable.
The earthing is provided with the following objectives
1. For the safety of equipment and personnel against lightning and voltage surges providing the discharge path for lightning arresters, gaps, and similar devices. Grounded neutral systems are provided by the ground connections.
2. The grounding of power systems is highly important. A substantial and adequate ground that will not burn off or permit a dangerous rise in voltage under abnormal conditions is essential. Extensive damage and danger arise when inadequate grounds have been provided.
In neutral earthing (or neutral grounding), the neutral points (star points) of star-connected 3-phase winding of power transformers, generators, earthing transformers are connected to low resistance ground. The major advantages of neutral earthing are:
(1) Each fault can be utilized to operate protective relays to isolate the fault.
(2)1nduced static charges are conducted to earth without disturbance.