Estimation of the cause of the frequent occurrence of multi-phase faults on transmission lines due to winter lightning

Abstract

In winter, the content (%) of “multi-conductor simultaneous faults” among “all the lightning faults” on double circuit transmission lines is much larger than in summer. To find a cause of the problem, many field investigations were conducted and statistics were collected. Based on these data, the author set up a new theory to estimate the probability of occurrence of multi-conductor faults during winter. This results coincide with the lightning performance of transmission lines either in summer or winter. The author's important view points which are newly introduced are followings; (1) The content (%) of large current lightnings among all the lightnings is much larger in winter than in summer (2) More than 83% of lightning flashes hit tower tops in winter, while only 25% hit tower tops in summer.