Improvement of Contamination Flashover Voltage Performance of Cylindrical Porcelain Insulators

Superior contamination flashover voltage performance of polymer insulators for transmission or distribution line is attributable not only to the hydrophobicity of silicone rubber housing material but also to their configurations. In the case of transmission or distribution line polymer insulators, core diameters are small and so the ratio of shed to core diameters is very large enough to improve the voltage distribution along the insulator owing to the divided and allotted voltages to its individual core portions having much higher surface resistances compared with shed portions due to the heavier leakage current density. We tried to improve the contamination flashover voltage performance of a porcelain long-rod insulator by applying hydrophobic silicone rubber coating only to all its core surfaces without coating shed surfaces and successful results have been confirmed. In this paper, contamination flashover voltage performances were evaluated among four kinds of specimens with different silicone rubber coatings by the salt fog test method. The detailed investigation results are presented.