Effects of shed configuration on AC flashover performance of ice-covered composite long-rod insulators

The flashover tests of artificially ice-covered composite long-rod insulators, including four types with a nominal voltage of 110 kV, four types of 220 kV and four types of 500 kV, were carried out in the multi-function artificial climate chamber. The result indicates that, firstly, icing flashover performance of the improved composite insulators for icing regions is not always superior to that of the standard composite insulators when icing is light. Meanwhile, Eh(flashover voltage gradient of dry arcing distance) first increases and then decreases with the increase of CF (creepage factor, namely the ratio of creepage to dry arcing distance). Secondly, when icing is moderate, the icing flashover performance is influenced by such main factors as shed diameter, shed spacing and the configuration of sheds with different diameters. In this situation, Ehof the improved composite insulators is higher than that of the standard composite insulators, and ice-covered composite insulator with three or four different shed diameters has better flashover performance than that with two different shed diameters. Thirdly, when icing is heavy, compared with the moderate icing condition, the difference of Eh between the improved composite insulators and the standard composite insulators diminishes. Finally, when icing is moderate or heavy, there is no obvious regular relation between CF and Eh.