Flashover Rate of Distribution Line Due to Indirect Negative Lightning Return Strokes

The flashover rate of a distribution line associated with indirect lightning flashes is investigated based on numerical calculations and statistical analysis by taking account of the correlation between the peak value and the front duration of negative return-stroke current waveforms. When the grounding interval of an overhead ground wire and/or surge arresters is 200 m, surge arresters are more effective than an overhead ground wire in suppressing flashover of the power lines, and installation of both is very effective. The flashover rate decreases if there is correlation between the peak and the front duration of lightning current; and it significantly decreases with the increase of the ground conductivity. When the line is equipped with surge arresters only, the flashover rate associated with subsequent strokes is higher than that associated with first strokes; and calculation with the fixed front duration of 2 mus for first stroke current does not always result in good estimates of flashover rate.