Analysis of insulation performance and polar effect of CF3I/CO2 mixtures

SF6 gas is widely used in power systems, however, it has a strong greenhouse effect. The search for a new environmentally friendly alternative gas has become an urgent task for the power industry. In this paper, CF
₃
I/CO
₂
gas mixtures in the ratio of 3:7 was tested based on a lightning impulse experimental platform. The 50% impulse breakdown voltage of CF
₃
I/CO
₂
gas mixtures was determined under various pressures (0.1~0.3MPa) and gaps (5~30mm) and compared to pure SF
₆
gas. The results indicate that CF
₃
I/CO
₂
gas mixtures has good insulation properties, reaching 0.84 times that of SF
₆
gas under slightly non-uniform electric field and 0.65 times that of SF
₆
gas in extremely inhomogeneous electric field. The polar effect of CF
₃
I/CO
₂
gas mixtures was also analyzed and the coefficient K is proposed to describe and compare the differences of 50% breakdown voltages under different electric field. The results show that the polar effect of CF
₃
I/CO
₂
gas mixtures under extremely inhomogeneous electric field is more obvious than that under slightly non-uniform electric field, and the polar reversal phenomenon occurs only under extremely inhomogeneous electric field. Considering various factors, CF
₃
I/CO
₂
mixtures has the capability of replacing SF
₆
gas in power equipment such as GIL.