Probability evaluation of low‐voltage distribution equipment lightning failures due to AC arc

Abstract

To construct low‐voltage power distribution systems, it is important to have correct information on the probability of failures by lightning to meet the requirement for high reliability of these systems. The burn‐out of low‐voltage distribution equipment is triggered by flashover due to lightning overvoltage followed by the arc discharge current at the commercial frequency voltage. The arc characteristics were investigated by superimposing the lightning impulse voltage across terminals of the low‐voltage distribution equipment connected to the commercial frequency power supply to reproduce these events on an experimental basis. As a result, it was found that the arc characteristics were affected by a number of factors. The probability of flashover occurrence on low‐voltage distribution equipment is determined based on the frequency distribution data of lightning overvoltage occurrence obtained by monitoring the surge counters on actual distribution lines. Then the probability distribution of arc currents is established by application of the forementioned experimental equation on arc characteristics. Finally, the method for evaluating damages by lightning to low‐voltage distribution equipment on actual lines was investigated with the frequency of lightning strokes and the configuration of low‐voltage distribution systems taken into consideration.