Experimental analysis of the feasibility of CF3I/CO2 substituting SF6 as insulation medium using needle-plate electrodes

CF₃I gas has low greenhouse effect and good insulation properties, so it can replace SF₆gas that has high greenhouse effect. In this study, the partial discharge inception voltage (PDIV) of CF₃I/CO₂ mixed gas is measured by power frequency test under different gas pressures, mixing ratios, and gap distances. The influence of these conditions on the partial discharge performance of CF₃I/CO₂ mixed gas is investigated. The PDIV of the CF₃I/CO₂ mixed gas is also comparatively analyzed with that of SF₆/CO₂ mixed gas. The results show that the PDIV of the CF₃I/CO₂ mixed gas is 1-1.2 times higher than that of SF₆/CO₂ mixed gas¿¿when the mixture ratio is between 10-30% and the gas pressure is between 0.1-0.3 MPa, which means the insulating ability of the CF₃I/CO₂ mixed gas is better than that of the SF₆/CO₂ mixed gas. By contrast, the PDIV of these two mixed gases exhibit similar variation trend with gas pressure when the mixing ratio is more than 20%. There is positive synergistic effect on the PDIV of CF₃I and CO₂. These results indicate that CF₃I/CO₂ (20 to 30%) mixed gas may be used to replace SF₆ gas for gas-insulated equipment applications.