The Development of SF6 Green Substitute Gas

Abstract

Due to its high greenhouse effect, the use of SF6 as the main insulating gas is restricted in the electric power field. Along with the aim of environmental protection, the search for new alternative gases with a lower greenhouse effect and higher insulation strength has received a lot of attention. The properties of alternative gases have a vital impact on the performance of medium-voltage power distribution equipment. Firstly, based on the existing liquefaction temperatures of SF6/N2, SF6/CO2, and SF6/CF4, the calculated liquefaction temperatures were expanded to 0.7 MPa. Combining the Antoine vapor-pressure equation and the basic law of vapor–liquid balance, the vapor pressures of SF6/N2, CF3I/N2, c-C4F8/N2, C4-PFN/N2, C4-PFN/CO2, and C5-PFK/CO2 were obtained. Secondly, the critical breakdown field strength was analyzed for C4-PFN/CO2, C5-PFK/CO2, SF6, CF3I/N2, C5-PFK/Air, and c-C4F8/N2. Finally, the GWPs of SF6/N2, C4-PFN/N2, C4-PFN/CO2, C5-PFK/CO2, and C5-PFK/N2 were discussed. The results show that the liquefaction temperature gradually decreases as the pressure rises; SF6/N2 has the highest vapor pressure at −5 °C; the critical breakdown field strengths of several mixtures are higher than that of SF6.