抄録
Surge arresters and distribution equipments with zinc-oxide (ZnO) elements are used for lightning protection of overhead power distribution lines in Japan. The increase of surge arresters including distribution equipments with ZnO elements has resulted in a remarkable decrease of lightning outages of distribution lines due to sparkover. On the other hand, these surge arresters are sometimes damaged by direct lightning strokes, especially in winter. Winter lightning strokes have very large electric charge as compared with summer lightning strokes. For improvement of surge arresters, we have measured the energy absorption capability of surge arresters using natural winter lighting strokes to a test tower. The energy absorption capability of an insulator with built-in ZnO elements is about 1.4 times larger than that of a surge arrester with the same ZnO elements. The ZnO elements of the insulator are wrapped in an insulation sheet in order to fix ZnO elements in the center of the porcelain housing because the insulators are installed horizontally. The insulation sheet strengthens insulation of the side of ZnO elements, and the energy absorption capability of the insulator improves. The result indicates that wrapping ZnO elements in the insulation sheet is one of effective countermeasures against surge arrester failures.
