Charge cluster triggers unpredictable insulation surface flashover in pressurized SF6

This paper reports an unpredictable insulation surface flashover phenomenon triggered by surface charge clusters under DC electric field, which is experimentally revealed by a donut-shaped dust cluster figure, presenting the outline of these surface charge clusters and showing a hollow donut-shaped structure interestingly. The charge cluster is randomly formed when ions originating from local micro-protrusions accumulate on the insulation surface, the edge of which produces a strong electrical field to induce local streamers. These local streamers provide an inducing factor, unpredictably triggering surface flashover. An in-depth illustration of how the dust phase transition depicts surface charge cluster evolution is proposed. This uncovered phenomenon has significant physical implications in revealing unpredictable insulation surface flashover and has great significance in further developing of HVDC gas insulated power transmission systems and other fields, such as microelectronics and space aircrafts.