Flashover performance of UHV&EHV post insulators under icing conditions

The results of a laboratory study on the electrical performance of 1000kV and 500kV post insulators as well as 500kV bushing covered with wet-grown ice were presented in this paper. The tests were performed in a large-scale artificial climate chamber at UHVAC test base of State Grid Corporation of China (SGCC). The ice formed artificially by super cooled water droplets accreted on the energized insulators under an air temperature of -10°C. The 50% flashover voltages and the leakage current were obtained by tests on polluted insulators during ice melting regime. The influence of salt deposit density (SDD) and the average diameter of the insulators to the flashover performance were discussed. The results show that the 50% flashover voltage is decreased with the increasing of SDD, which follows the law of negative power exponent. And a larger diameter of insulator corresponds to a larger icing area when the icing condition is the same, which result a smaller resistance on the surface of the insulator. Therefore, in a fixed SDD, the 50% flashover voltage also decreased with the increasing of the average diameter, but the leakage current before flashover is larger, which can be explained by ohms law.