Lightning strike accident analysis and modification measures for incoming lines of power grid in a mining area

In view of the accident of main transformer being broken due to tower at incoming lines of Tunlan substation caused by lightning strike, the problems of lightning protection measures of the incoming lines were analyzed and researched. The research results show that the lightning protection of the incoming lines has problems such as excessive grounding resistance of the tower, too high lines insulation level, and mismatching between action value of arrester and lines insulation level. In view of the existing problems and hidden dangers, the following modification measures were proposed: optimize impulse grounding of the tower at incoming lines by using dendritic radioactive grounding body; use adjustable overvoltage protection gap to match lines arresters on the terminal tower, so as to form refined comprehensive protection of the incoming lines; install gap-free zinc oxide arrester on the terminal tower at incoming lines. The ATP-EMTP simulation results show that the combined effects of the three modification measures can effectively reduce amplitude and steepness of lightning intruding wave and ensure safe operation of the mine power grid.