Abstract
Spatial distribution of lightning discharges that were observed simultaneously with faults of power transmission lines in Hokuriku area in winter is analyzed. Spatial distribution of all lightning discharges located by LLS in winter around the coastline of the Sea of Japan is analyzed as well for comparison. Majority of the transmission line faults experienced within about 20km from the coastline were associated with positive flashes. On the contrary, most of the faults located inland farther than about 20km from the coastline were associated with negative upward flashes. Distribution of located lightning flashes dependent on their polarities observed by LLS coincides with this pattern of lightning faults. Accordingly, the relationship between the lightning flash density observed by LLS and the frequencies of lightning hits on high structures in winter is examined. Based on this result, the lightning fault rate of 500kV transmission lines in winter is evaluated by using this relationship, resulting in successful reproduction of the high fault rate experienced so far.
