Abstract：Overhead transmission lines are distributed in the wild, even a considerable part of Most of the transmission lines area lie in the countryside and mountain area, the geographical environment and climatic conditions of which are harsh. In summer, the alternate often times when the thunder storm weather, then greatly increases the number of times. In this paper, the main cause of lightning trip-out failure and fault location are highlighted for an actual line tripping accident On July 13, 2012, combined with fault inspection, the weather of that day,the data of lightning measuring and orientation system and the calculation of protection level. Finally, the corresponding preventive measures are stated based on cause and problems exposed of the accident in the article in order to avoid such failure , moreover insure grid running safety and reliability.
2014, Vol. 15 
