Study on the DC Flashover Performance of Various Types of Insulators With Fan-Shaped Nonuniform Pollution

In areas with heavy dust or continuous wind in a single direction, fan-shaped nonuniform contamination at the windward and leeward side of the insulator string may affect flashover performance. In this paper, dc pollution flashover tests of insulators under fan-shaped nonuniform pollution were presented, and a comparison of flashover performance among 7-unit suspension insulator strings with four different disk profiles was made. Then, the influence of fan-shaped nonuniform pollution on flashover voltage, arc propagation, and critical leakage distance were investigated. Research results indicate that the insulators with different types were influenced variously on their flashover stress, utilization rate of creepage distance, and critical leakage distance by fan-shaped nonuniform pollution. A reduction in the ratio W/L of windward to leeward side salt deposit density (SDD) from 1/1 to 1/15 gave a median 35% ± 4% decrease in flashover strength. The extrapolation of results for the seven-unit strings suggests that some increment in shed space or structure height of the insulator can be preferable in dc transmission lines where there is fan-shaped nonuniform pollution accumulating at the windward and leeward side of the insulator string.