Insulation characteristics of CF3I/c-C4F8/N2 gas mixtures in slightly non-uniform electric field

Abstract

In this paper, power frequency breakdown tests as well as positive and negative lightning impulse breakdown tests have been performed. The breakdown voltages of CF 3 I/CO 2 /N 2 , c-C 4 F 8 /CO 2 /N 2 , CF 3 I/c-C 4 F 8 /CO 2 gas mixtures have been measured in different gas pressures, mixing ratios and electrodes distances in slightly non-uniform electric fields. In addition, the breakdown voltages of CF 3 I/c-C 4 F 8 /CO 2 gas mixtures have been comparatively analyzed with SF 6 /CO 2 , CF 3 I/CO 2 , c-C 4 F 8 /CO 2 gas mixtures. The results show that CO 2 is excellent buffer gas to CF 3 I and c-C 4 Fρ as it has synergistic effect. The power frequency breakdown voltages of CF 3 I/c-C 4 F 8 /CO 2 gas mixtures are basically the same as that of c-C 4 F 8 /CO 2 gas mixtures, which are higher than that of CF 3 I/CO 2 gas mixtures. Besides, the 50% breakdown voltage of c- CρFρ/CFρI/CO 2 gas mixtures under lightning impulse are higher than that of CF 3 I/CO 2 . Compared with SF 6 /CO 2 gas mixtures, CF 3 I/c-C 4 F 8 /CO 2 gas mixtures have the same insulating performance in short electrode distance, and show more excellent insulating ability at an electrode distance more than 20mm.