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 N₂. In this paper, breakdown performance of CF₃I/N₂ gas mixtures, SF₆/N₂ 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%N₂ gas mixtures present similar insulation properties as 20%SF₆/80%N₂ gas mixtures. Considering liquefaction temperature and insulation properties, 30%CF₃I/70%N₂ gas mixtures could be possible substitutes to SF₆ or SF₆/N₂ gas mixtures in low pressures, and it is significant to study their insulation strength in higher pressures.