Effect of electrical test methods on dc flashover performance of ice-covered ceramic insulators

In artificial icing tests, three test methods are frequently used for evaluating the electrical characteristic of ice-covered insulator strings, they are: average flashover voltage method (AM), 50% withstand voltage method (WM) and minimum flashover voltage method (MM). Based on measurements of DC flashover characteristics of ice-covered porcelain and glass suspension insulators in an artificial climate chamber, this paper studied the influences of various test methods on DC flashover voltage of insulators. Test results revealed that the average flashover voltage (U_ave obtained using AM) is the highest, followed by the 50% withstand voltage (U_50% obtained using WM). The minimum flashover voltage (U_fmin obtained using MM) is the lowest. The fitting formulas between DC flashover voltage (U_f) and conductivity of the icing water (γ₂₀) are consistent for the three test methods. Moreover, the differences on exponent b characterizing the influence of conductivity of the icing water (γ₂₀) on the flashover voltages are not remarkably different for the three electrical evaluation methods.