Experimental Study on Power Frequency Breakdown Characteristics of C 4 F 7 N/CO 2 Gas Mixture under Quasi-Homogeneous Electric Field

Abstract

As a new environmental-friendly gas insulating medium, perfluoroisobutyronitrile (C 4 F 7 N) has been widely concerned in recent years due to its relatively low global warming potential and excellent dielectric strength, which has the potential to replace the most greenhouse gas, sulfur hexafluoride(SF 6 ). However, there are a few systematic studies on the influence of gas pressure and mixing ratio on the dielectric strength of C 4 F 7 N/CO 2 gas mixture at present. In this paper, the power frequency breakdown characteristics of C 4 F 7 N/CO 2 gas mixture under different pressure and mixing ratio conditions were tested using the gas insulation performance test platform. The optimal mixing ratio and pressure range of C 4 F 7 N/CO 2 gas mixture for engineering application were also discussed. It is found that the breakdown voltages of C 4 F 7 N/CO 2 gas mixture show a saturated growth trend with gas pressure and mixing ratio. The breakdown voltage of the gas mixture with 10% C 4 F 7 N can reach 80% of pure SF 6 under the same condition. The insulation performance of the gas mixture with 20% C 4 F 7 N can reach more than 95% of pure SF 6 . Relevant results indicate that the gas mixture with 4%-12% C 4 F 7 N has the potential to be applied to high-voltage gas-insulated equipment.