Research on icing flashover test methods and leakage current analysis of full-scaled insulator strings

Icing flashover performance of insulator strings for UHV transmission lines is usually obtained by diverse test methods, but mostly based on the method of raising voltage to a flashover, including the method recommend in IEEE Std. 1783-2009. An icing flashover test method was proposed in this paper in consideration of the disadvantages and merits of existing methods. With the recommended method, full-scaled insulator strings are energized under a constant test voltage during icing, hardening and melting period until a flashover occurs or withstands. And then an Up-and-Down method is utilized to obtain the 50% flashover voltage. Then icing flashover test results obtained by this recommended method and IEEE method are compared by flashover voltage and arc & leakage current characteristics. It shows that the average flashover voltage obtained by IEEE method is about 17% higher than U_50% obtained by the method recommended in this paper, while the deviation is much higher too. And from arc developing point, the withstanding process with a constant voltage provides a condition that arcs may develop by nature, which make this method fit the reality of operating insulators better. In conclusion, the test method recommended in this paper is more suitable for icing flashover tests and outdoor insulation design.