Characteristics of Lightning Impulse Flashover of Rod-to-Rod Gap and Suspension Insulator in Thundercloud in Winter

Abstract

Double-circuit faults of transmission lines of often occur in winter in Japan. One of the causes for such faults in winter has been thought the reduction of the flashover voltage under the influence of space charge with the presence of ice crystals or water in the thundercloud. In this paper, we describe the result of the flashover experiment which was performed with a rod-to-rod gap or a suspension insulator in thunderclouds at the top of a mountain of about 1, 000m in altitude in winter. Summary of the results is as follows.
(1) The change of the lightning impulse flashover voltage of rod-to-rod gap in the thundercloud with rain is less than 3% in comparison with the flashover voltage in rain.
(2) The lightning impulse flashover voltage of a suspension insulator in the thundercloud with rain in the negative electric field is 7% less in comparison with the flashover voltage in rain, and 13% less in comparison with that under fine weather.
(3) The lightning impulse flashover voltage of a suspension insulator in the thundercloud with snow in the negative electric field is 9% less in comparison with the flashover voltage in snow, and 22% less in comparison with that under fine weather.