Hydrophobicity and insulated resistance of composite insulators with biological contamination

Biological growth has been observed on insulators installed all over the world. However its impact on the electrical performance is not well known. This paper described the investigations on the performance of post insulators with biological growth at a converter station. Both the ceramic and composite insulators were investigated. Two kinds of biological agents, lichen and mold were found on the composite insulator surface, but interestingly, no biological agent was found on the surface of ceramic insulators in the same environment condition. Lichen concentrated on the upper surface and mold on the lower surface. It seemed that the impact of lichen growth on the hydrophobicity is low, but hardly no hydrophobicity when mold growth. In addition, the insulated resistance test was carried out on the biologically contaminated insulators with and without salt water. Results show that whatever the surface was dry or not, high resistance were obtained with only less biological agent growth at the edge of insulators, but declined sharply when most of the surface was covered with lichen and mold. Therefore, it is strongly recommended to remove the mold, with which most the insulator surface is covered.