INFLUENCE OF TRACE SF₆ ON STREAMER CORONA DEVELOPMENT IN SF₆/N₂ MIXTURES UNDER POSITIVE DC VOLTAGES

SF6/N2 is a kind of binary gas mixtures with synergistic effects, that is, a small amount of SF6 can make the gas mixtures maintain the useful characteristics of an electronegative gas. This paper focuses on the study of the influence of trace SF6 on streamer corona development in SF6/N2 mixtures under positive DC voltages. A needle-to-plane electrode corona discharge experimental setup was set up. Considering that the streamer corona development was more significant at atmospheric pressure, the streamer corona light emission images under different SF6 content at 0.1 MPa were given. The corona characteristics in SF6/N2 mixtures including corona onset characteristics and current pulse characteristics were compared between atmospheric pressure and high pressure (0.3 MPa). The experimental results have shown that both the length of streamer channel and the number of bifurcation at streamer head decrease with increasing SF6 content. Within the experimental scope, with increasing SF6 content, the pulse-time parameters decrease, while the positive corona onset voltage and pulse-repetition rate increase.