Partial discharge and breakdown mechanisms in ultra-dilute SF6and PFC gases mixed with N2gas

Because of the high global warming potential of SF 6 gas, research on alternative gases for electrical insulation with a lower environmental impact is essential. Gas mixtures composed of electronegative gases and N 2 gas have the advantage of the reduction of the amount of SF 6 gas and of utilizing the synergistic effect in electrical insulation performance. We investigated the partial discharge (PD) and breakdown (BD) characteristics of SF 6 /N 2 and PFC (C 3 F 8 /N 2 and C 2 F 6 /N 2 ) gas mixtures under non-uniform electric field conditions, by changing the dilute content of electronegative gases. As a result, the synergistic effect in SF 6 /N 2 gas mixtures was verified to be higher than that in PFC/N 2 gas mixtures. The physical mechanism from PD inception to BD was discussed with consideration of the difference in electronegativity of SF 6 and PFC gases. Furthermore, we found that PD inception and PD-to-BD mechanisms changed at a content of 10 ppm for SF 6 due to the electron attachment activity of SF 6 gas. The change in the PD and BD mechanisms in C 3 F 8 /N 2 and C 2 F 6 /N 2 gas mixtures appeared at 0.1% content for C 3 F 8 and at 1% content for C 2 F 6 .