Needle-plane Configuration Research Articles

Anomalous creeping flashover characteristics in N/sub 2//SF/sub 6/ mixed gas under single pulse voltage

Creeping flashover characteristics for the needle electrode-plane electrode filled with N/sub 2//SF/sub 6/ gas mixtures have been investigated. In the case of the needle-plane configuration, the flashover voltage was enhanced by an admixture of SF/sub 6/ into N/sub 2/. On the other hand, by the insertion of a solid dielectric barrier between the needle and the plane, only the negative creeping flashover voltage was reduced drastically by the admixture of SF/sub 6/ gas into N/sub 2/ gas, and a highly emissive region at the top of a creeping corona was found in N/sub 2//SF/sub 6/ gas mixture. This behavior is strongly affected by the creeping corona extension process, depending on the creeping distance and the gas pressure.

Detection of Non-Destructive Pulse Currents in Polyethylene Prior to its Dielectric Breakdown

Prebreakdown, non-destructive current pulses were observed in a solid dielectric under ac voltage stress for the first time. They were detected in polyethylene using a needle-plane configuration. The needle electrode was made of carbon-filled polyethylene, to improve contact with bulk polyethylene. The observed charge pulses were less than 1 pC in magnitude, and appeared well in advance of dielectric failure or tree formation.