Aging characteristics and influencing factors of the sheds of composite insulators in karst regions of China

In recent years, more and more high-voltage overhead transmission lines were built passing through the karst regions in southwestern China. This type of special landform seems to have an adverse effect on the aging of the sheds of the line suspension composite insulators, which may lead to unexpected flashover and line tripping. In order to find out the particularity of the aging characteristics of insulators operating in the karst regions, sam-ples in operation were selected from both the karst regions and the flatlands. Hydrophobicity, amount of surface contamination, and contaminant composition of the sheds were studied, then a comparison of performance between the two was made, and the possible influencing factors that cause such differences were discussed. The results show that the overall aging of the sheds of the composite insulators operating at the karst regions is more aggravated, which is caused by the combined influence of factors including the special topography, cli-mate, and pollution in the area. The strong wind crossing the col will bring about the mutual scraping on the edges and stress concentration at the root of the sheds, leaving scratches and root cracks; the infiltration from these rupture of acid liquid, if any, will accelerate the aging and corroding of the internal silicone rubber material; moreover, the carbonates enriched on the surface of the sheds will gradually transform into more corrosive sul-fates in an acidic environment, leading to further deterioration and chalking of the sheds of the insulators. The research work in this paper can provide guidance for the current operation and maintenance of composite insulators in the karst areas, as well as having important reference values for the layout design and insulation configuration of transmission lines to be built across karst landforms in the future. © 2021, Tech Science Press. All rights reserved.