Distribution arrester failures caused by lightning current flowing from customer's structure into distribution lines

Distribution arrester failures have been thought to be caused by direct or nearby lightning strokes. We have, however, found that distribution arreste r failure is caused by part of the lightning current which flows into distr ibution lines when the customer's structure is struck by lightning. We call this current "lightning backflow current". In order to clarify the influen ce off lightning backflow current on arrester failure, we have conducted ex perimental and analytical studies and observed the distribution outages. Th e main results are as follows. (1) The calculated failure probability of an arrester caused by lightning b ackflow current in winter is almost equal to that caused by a direct lightn ing stroke to distribution lines. (2) According to the investigation of lightning-caused failures; about half of the arrester failures are due to lightning backflow current. (3) Lightning backflow current should be considered as one off the main cau ses of distribution arrester failures.