Study on dry band discharge of wet polluted surface with float potential metal by electro-thermal synchronous observation

Abstract

Severe partial arc occurred near metal bolts on the composite tower under wet pollution conditions, which had a close relationship with the temperature distribution on the surface. Artificial contamination tests on the small-sized composite plate were carried out. Temperature distribution and leakage current variation of the specimen were acquired synchronously. The effects of float potential metal, pollution layer width, metal shape, and moisture on temperature distribution, dry band formation, and discharge phenomenon were studied by a series of comparative experiments. The results show that the float potential metal makes the temperature distribution of the pollution layer more concentrated. The dry band begins to form in the region with the highest temperature. The formation of a dry band on the narrow pollution layer is faster. The temperature of the dry band endpoint is very high and increases with the extension of the dry band. The formation and passing through of dry band blocks leakage current leading to the occurrence of partial arc. Temperature distribution near metals with sharp shapes is more inhomogeneous. In a humid environment, dry band arc can exist stably and develop to float potential metal. Owing to the rewetting of the dry band, dry band formation, and dry band arc will occur repeatedly.