The Development of SF 6 Green Substitute Gas

Due to its high greenhouse effect, the use of SF 6 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 SF 6 /N 2 , SF 6 /CO 2 , and SF 6 /CF 4 , 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 SF 6 /N 2 , CF 3 I/N 2 , c-C 4 F 8 /N 2 , C4-PFN/N 2 , C4-PFN/CO 2 , and C5-PFK/CO 2 were obtained. Secondly, the critical breakdown field strength was analyzed for C4-PFN/CO 2 , C5-PFK/CO 2 , SF 6 , CF 3 I/N 2 , C5-PFK/Air, and c-C 4 F 8 /N 2 . Finally, the GWPs of SF 6 /N 2 , C4-PFN/N 2 , C4-PFN/CO 2 , C5-PFK/CO 2 , and C5-PFK/N 2 were discussed. The results show that the liquefaction temperature gradually decreases as the pressure rises; SF 6 /N 2 has the highest vapor pressure at −5 °C; the critical breakdown field strengths of several mixtures are higher than that of SF 6 .