Flashover characteristics of a hydrophobic surface covered by water

Due to their hydrophobic properties, composite insulators have excellent anti-pollution flashover performance and have been widely used in power systems. For a better understanding of the flashover characteristics of a hydrophobic surface at wet conditions, the hydrophobic surface is covered with water droplets and water film, respectively, in this paper. The initiation and development of partial arc are observed by an ultrahigh-speed camera and the leakage current is also recorded. It is found that there exists a critical water proportion for a given dry band length and water volume conductivity. Beyond this water proportion, the partial arc does not necessarily lead to the flashover. On the contrary, flashover will take place right after the occurrence of partial arc. Furthermore, it is also found that when the water proportion is below the critical water proportion, the flashover voltage is barely related to the volume conductivity and the flashover voltage generally decreases with the increase of water volume and water droplet number. The results obtained are of great significance to understand the flashover process of hydrophobic surfaces.