Anomalous creeping flashover characteristics in N/sub 2//SF/sub 6/ mixtures and effect of barrier surface

Creeping flashover characteristics have been investigated for an N/sub 2//SF/sub 6/ composite insulating system consisting of insertion of an insulating barrier between the needle electrode and the plane electrode. The negative flashover voltage (FOV) for the flat and stepped systems in N/sub 2/ (D=0%) is as high as that of SF/sub 6/ (D=0%) by the effective field relaxation from the accumulated charges. Remarkable reduction of FOV induced by few percentages SF/sub 6/ addition should originate from the barrier interaction such as ineffective charge accumulation and photon-related emission. However, for the grooved system, the confinement effect should be effective, resulting in lower FOV in N/sub 2/.