Physical Stages Dividing and Quantitative Study of Insulator Surface Discharges

The surface discharges of polluted insulators have different discharge forms and characteristic parameters at different stages. The surface discharges and flashover phenomena were simulated via series of high voltage experiments, in which the discharge images of each stage and photons number were recorded by visible light camera and ultraviolet imaging meter respectively. At the same time, the discharge quantities and the leakage current waveforms were measured by partial discharge measuring instrument and oscilloscope. According to different forms of discharge, the physical stages of insulator surface discharges were divided into corona discharge, glow discharge, mixed transition stage, intermittent arc and continuous arc stage. Then photons number, discharge quantities and leakage current waveforms were synchronized on the time scale for each stage. The relationship between photons number and discharge quantities was investigated by the fitting method. The box transform method in fractal theory was applied to extract the fractal dimension of leakage current waveform. They quantified the dividing of each stage of surface discharges and provided more comprehensive characteristic indexes for the forecasting of contamination flashover.