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Influence of barrier thickness on discharge behavior in air gap with GFRP insulator under impulse voltage stress

The barrier effect is well known to increase the breakdown voltage of air gap. While, previous research has suggested that the occurrence of secondary discharge at the underside of barrier accompanied by the development of upper surface corona discharge on the barrier contributes to the reduction of the barrier effect. The properties of the underside discharge are, however, still not well understood. This paper presents the backside discharge phenomenon and the influence of barrier thickness on discharge behavior in air gap with solid insulator, especially pertaining to the occurrence of underside discharge. In the experiment, a GFRP board was used as insulation barrier, positive or negative steep impulse voltage was applied to needle-plane short gap with insulation barrier in atmospheric air, the second discharge occurred at the backside of the barrier in response. The spatiotemporal changes of discharge luminescence at underside of barrier were observed by ICCD camera.