Study of lightning protection of power distribution lines located in mountainous areas

We have investigated the characteristics of lightning outages on power distribution lines located in mountainous areas facing the Sea of Japan. Analytical studies have been carried out to establish better protection methods for these lines. Most of the outages are caused by lightning current flowing into distribution lines from a tall structure struck by lightning. Protection for poles supplying power to a tall structure should be emphasized. Surge arresters on the lines constitute the large part of damaged equipment. Installing an overhead ground wire can reduce the failure probability of an arrester to about 30%. When an overhead ground wire is installed on distribution lines, increasing the withstand capability of arresters from 2.5 kA rated arresters to 5 kA rated ones is effective; this can reduce the failure probability to less than 50%. Based on the results, protection design procedures against lightning are proposed for power lines.