Surface flashover characteristics of GIS insulator attached with metal particle under power frequency voltage superimposed lightning impulse

SF6 gas insulated switchgear (GIS) is widely used in modern power system, but there are problems on stability due to its large-scale application. Among these problems, the insulator flashover fault is the most frequent problem. Hence, in order to investigate the characteristics of surface flashover of GIS insulator attached with metal particle, an experimental platform of power frequency voltage superimposed lightning impulse was set up and the waveform of positive lightning superimposed on the negative peak of power frequency voltage was generated. At the same time, an electric field simulation model of sample was set up. It was found that when the amplitude of power frequency component was less than 30kV, the surface flashover voltage of insulator attached with metal particle under the superimposed waveform showed obvious plateau phenomenon, when the flashover voltage was almost the same as that under lightning impulse alone. However, when the amplitude of power frequency increased to 40kV, the surface flashover voltage suddenly dropped by 10% around. By comparing with elecrtric field distribution of the sample, it was speculated that the above phenomena were directly related to the partial discharge near the insulator surface caused by distorted electric field for the attachment of metal particle.