Analysis of the flashover process on ice-covered insulator string

In order to reveal the mechanism of discharge on icing insulators, the flashover process during ice-melting period of polluted and ice-covered insulator string was experimentally studied . Arc development, evolution of leakage current and its frequency representation were analyzed typically. The results indicate that the flashover process can be divided into five stages, namely, initial stage, intermittence local arc stage, arc propagation stage, critical flashover stage and flashover stage. Each stage has distinct discharge phenomenon and a fixed level of leakage current peak value. Both the nonlinearity and the phase angle difference between leakage current and the applied voltage decrease with the raising of leakage current. At the initial stage, the leakage current peak value is less than 10 mA and hardly has any harmonic content. When the arc is intermittent, the harmonic content of the leakage current is the largest. The leakage current waveform is smooth and has fewer harmonics on pre-flashover status. And the pre-flashover current increases with the increasing of salt deposit density (SDD).