Study of the flashover process on ice-covered insulator string

The flashover process during ice-melting period of polluted and ice-covered insulator string was studied by experiment in this paper. Arc development, evolution of leakage current and its frequency representation (FFT) were analyzed. The results indicated that the flashover process can be divided into five stages, named 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 10mA 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 at critical flashover stage.