Investigations on AC pollution flashover performance of insulator string under different non-uniform pollution conditions

Observations of contamination tests showed that, the contamination distribution of insulators is usually uneven. In this study, the solid layer method was used to imitate different non-uniform pollution conditions and the AC pollution flashover tests of 7-unit insulators were carried out. The results indicate that the increase of uneven pollution degree J from 1 to 15 will give a 39% raise of U 50 under non-uniform pollution on top and bottom surfaces, a 23% decrease for fan-shaped non-uniform pollution and a 21% higher U 50 with ring-shaped non-uniform pollution. A higher occupation ratio (k) of leeward side will reduce U 50 under fan-shaped non-uniform pollution and a bigger radius R of heavy polluted area has certain effect on U 50 for ring-shaped non-uniform pollution. The U 50 and salt deposit density still can be expressed by the negative power function, and non-uniform pollution conditions and J have great effect on a, but less impact on n. The correction equations of different non-uniform pollution conditions are obtained and the relative errors are acceptable. The research has certain reference significance for the design and selection of AC transmission line external insulation.