Flash-over mechanism of SF6-gas type termination for DC power cable

With the development of ±250 kV DC-XLPE power cable and flexible joint so far, there arose a need to develop other components for the construction of DC-power transmission. One of those is SF₆ -gas type, horizontally installed termination. To supply the DC electric power with reliability and stability, we need to clarify the phenomena under DC voltage application in this system. This paper examines the flash-over (FO) phenomena under DC voltage application in the SF₆-gas type, horizontally installed termination by using the model electrode in which the firefly of metal particle was imitated under the condition of charge accumulation on the epoxy bushing. In this examination, we confirmed experimentally that the behavior of metal particles was affected by the change of a field distribution due to the charge accumulation on the epoxy bushing, on the other hand, the metal particle promoted the charge accumulation on the epoxy bushing. Under these circumstances, FO initiated at the edge of the metal particle showing firefly, developed along the epoxy bushing surface. These seemed to mean that there was a synergetic effect of charges accumulation and behaviors of metal particle to introduce a FO. It was concluded that it was very important to be strongly aware of the existence of metal particles and its behavior in the SF₆-gas type termination, when it was used under DC voltage application