The difference of pollution flashover performance between silicone insulator and porcelain insulator is reflected in each stage of pollution flashover. In the pollution accumulation stage, the composite insulator shed shape would help reduce the pollution due to its simple and no edge underneath design. However, because of the high surface resistivity of the composite insulator, the sheath of the shed is easily charged due to the friction with the particles in the atmosphere, it would easily absorb ash, which is unfavorable to reduce the pollution.
Under damp environment , due to the mobility of hydrophobic of silicone insulator, the fouling layer become hydrophobic as well, and the surface of the water droplets separate each other, can not form a continuous film of water, the leakage current of silicone insulator is much lower than the porcelain insulator under the same filthy degrees. It is essential for enhancing flashover voltage of the silicone insulator.
However, under long term raining and damp condition, the hydrophobicity of silicone rubber may be temporarily reduced or even seriously decreased. At this time, the shed of silicone insulator will give positive and obvious influence on the flashover voltage.