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 SF6 gas 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.