Discharge characteristics of CF3I/N2 mixtures under lightning impulse and alternating voltage

As the greenhouse effect of SF6gas, the research on seeking alternative insulating gas to SF6has become an imperative case. CF3I and its mixtures have been considered as the most promising insulating gas to replace SF6gas. In this paper, the discharge characteristics of gas gap and insulator in CF3I/N2gas mixtures under lightning impulse and alternating voltage were investigated. The effect of voltage, pressure as well as decomposition product after flashover were studied. Experimental results showed that in inhomogeneous electric field the breakdown voltages of CF3I/N2with 30% CF3I gas is lower than SF6/N2mixtures with 20% SF6. However, the flashover voltage of insulator in CF3I/N2is higher than that in SF6/N2mixtures. When compared to CF3I/N2itself, the 50% breakdown voltage under positive lightning impulse were lower than that under negative lightning impulse. The CF3I/N2gas mixtures with insulator also had polarity effect and appear polar reversal phenomenon. Under lightning impulse, there is no decomposition product on the surface of insulator after flashover but under alternating voltage, obvious iodine was produced on the surface of insulator.