AC Flashover Performance of Glass Insulators Covered with Ice or Snow at Natural Station

The electrical performance of insulators will be weakened remarkably under coexisting low pressure, icing and pollution, so icing flashover performance is one of the key criteria for isolator selection of external insulation for transmission lines at high-altitude areas. Instead of studying icing flashover in artificial simulation environments, which is the most common situation among related researches, we tested the AC electric characteristics of long-string LXHY3-160 insulators at a field site at 1 400 m of altitude, and then we analyzed the influence of snow on the flashover characteristics. The solid layer method was used to prepare the samples while the even-rising voltage method was adopted for electric tests. The test results show that a thin layer of snow covers the insulator samples, while ice with density of 0.775 4 g/cm3mainly distributes at windward side of insulators. The conductivity of ice water during flashover is high, and it increases with length insulator string, yet it is basically the same and has nothing to do with string length when the ice on the insulator strings is melt completely. The influence of the snow/ice on flashover performance at high altitude is consistent with the conclusions obtained in artificial chambers. For insulators covered with snow or ice, flashover voltage is nearly linear to string length, while the ice amount on insulator strings has a linear regression relation to string length.