DC pollution flashover performance of HVDC composite insulator under different non-uniform pollution conditions

The non-uniform air flow field and electrical field distributing around insulators cause uneven deposition of pollution particles on different positions and parts of the insulator surfaces. Pollution-induced flashover is a serious threat to the safe operation of the power system, and non-uniform pollution distribution has great influence on flashover voltage of insulators. Towards this, in this study, the solid layer method was used to simulate different non-uniform pollution conditions. Then, DC pollution flashover tests of composite insulators were carried out and the flashover performances were analyzed. The results indicated that the increase of K uw (from 1 to 15) decreased U-50 by 27-32%. While the increase of K-T/B (from 1 to 10) increased U-50 by 35%, and the increase of K-H/M (from 1 to 4) increased U-50 by 25%. Where K-L/W, K-T/B and K-H/M are the SDD (salt deposit density) ratio of windward to leeward side, top to bottom surface and high voltage to middle group respectively. Besides, higher proportion of leeward side area will reduce U-50. U-50 and SDD are still in agreement with the negative power function relationship, non-uniform pollution conditions have great effect on a (constant of power function), but less impact on n (characteristic index of power function). Finally, equations for calculating different non-uniform pollution flashover voltages were established and validated, also the relative errors are acceptable. The results are very important for guiding insulation design and anti-pollution works of operating transmission lines.