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

In this paper, power frequency breakdown tests as well as positive and negative lightning impulse breakdown tests have been performed. The breakdown voltages of CF3I/CO2/N2, c-C4F8/CO2/N2, CF3I/c-C4F8/CO2gas 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 CF3I/c-C4F8/CO2gas mixtures have been comparatively analyzed with SF6/CO2, CF3I/CO2, c-C4F8/CO2gas mixtures. The results show that CO2is excellent buffer gas to CF3I and c-C4Fρ as it has synergistic effect. The power frequency breakdown voltages of CF3I/c-C4F8/CO2gas mixtures are basically the same as that of c-C4F8/CO2gas mixtures, which are higher than that of CF3I/CO2gas mixtures. Besides, the 50% breakdown voltage of c- CρFρ/CFρI/CO2gas mixtures under lightning impulse are higher than that of CF3I/CO2. Compared with SF6/CO2gas mixtures, CF3I/c-C4F8/CO2gas mixtures have the same insulating performance in short electrode distance, and show more excellent insulating ability at an electrode distance more than 20mm.