Influence of electric field non-uniformity on breakdown characteristics in SF6/N2 gas mixtures under lightning impulse

For the application of SF
₆
/N
₂
in power equipment such as GIS and GIL, the breakdown characteristics of SF
₆
/N
₂
in varying electric field non-uniformity under standard lightning impulse were studied in this paper based on a lightning impulse experimental platform. The research indicates that the reversal of polarity effect appears in SF
₆
/N
₂
gas mixtures. That is, when the pressure is relatively low, the 50% breakdown voltage under positive polarity is lower than which under negative polarity. When gas pressure reaches the critical pressure, the situation would be opposite. The augment of SF
₆
mixing ratio or decrease of electric field non-uniformity would both result in the decline of the critical pressure. Meanwhile the change of polarity effect with SF
₆
/N
₂
is later than that with pure gas with the increase of electric field non-uniformity. In addition, the phenomenon of critical radius of SF
₆
/N
₂
gas mixtures was found. The critical radius reduces with the increase of gas pressure and is smaller under positive lightning impulse than negative. And the phenomenon of critical radius with pure gas is more obvious than that with gas mixtures.