Breakdown Characteristics of CF3I and CF3I/N2 Gas Mixtures in Uniform Field

With its high insulation capability and excellent environmental friendliness, CF3I has been considered as a potential substitute to SF6. However, considering its high boiling point, CF3I should be mixed with buffer gases such as CO2 or N-2. In this paper, breakdown performance of CF3I/N-2 gas mixtures, SF6/N-2 gas mixtures and pure SF6 gas in uniform field are investigated, with negative dc voltage or negative lightning impulse voltage applying. DC breakdown experiments of pure CF3I gas and pure SF6 gas show that the dielectric strength of CF3I is not always higher than that of SF6. The insulation experimental results show that in low pressures, 30% CF3I/70%N-2 gas mixtures present similar insulation properties as 20%SF6/80%N-2 gas mixtures. Considering liquefaction temperature and insulation properties, 30%CF3I/70%N-2 gas mixtures could be possible substitutes to SF6 or SF6/N-2 gas mixtures in low pressures, and it is significant to study their insulation strength in higher pressures.