Protection provided by ground wire against induced lightning surges on distribution lines

摘要

Overhead distribution lines are subjected to direct lightning strokes as well as induced lightning surges caused by the lightning strokes in the vicinity of the lines.A lightning stroke to an overhead ground wire will usually produce a back flashover to the phase conductors at the clearances used for distribution lines.As the shielding effect of an overhead ground wire on distribution lines is very limited it is rarely used to intercept the direct lightning strokes.Therefore,the ground wire need not be located above the phase conductors less than 500 kV.~1,2.These surges are not a threat to 69 kV and above power lines. However,they can cause outages and damage to equipment on 34.5kV and below distribution lines.Flashovers on distribution lines up to 34.5 kV level caused by the induced voltages is much more frequent than the flashovers caused by the direct lightning strokes.The number of ourages and damage to equipment on these lines can be decreased if the magnitude of the inducedvoltage surges caused by lightning is reduced.