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 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
F
₈
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- C
₄
F
₈
/CF
₃
I/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.