Breakdown and decomposition characteristics of environmentally friendly C4F7N/N2/O2 gas mixture at high pressure

C 4 F 7 N gas mixture has excellent insulating property, which is a gas insulating medium widely concerned by scholars at home and abroad in recent years. In order to reduce the harmful solid by-products produced during the discharge process, a certain amount of O 2 should be added to the C 4 F 7 N/N 2 gas mixture. This paper investigated the potential of C 4 F 7 N/N 2 /O 2 gas mixture in high-voltage gas insulating electrical equipment, tested the breakdown characteristics of C 4 F 7 N/N 2 /O 2 gas mixture containing oxygen of different volume fractions under 0.6MPa by gas insulation test platform, and analyzed the decomposition products and contents of the gas mixture after breakdown by GC-MS. It is found that adding a certain amount of O 2 to the C 4 F 7 N/N 2 gas mixture can improve the insulation self-recovery performance under high pressure, the main decomposition products of C 4 F 7 N/N 2 /O 2 gas mixture after multiple breakdowns are CF 4 , C 2 F 6 , C 3 F 6 , C 3 F 8 , CF 3 CN, C 2 F 5 CN, CO, COF 2 , C 2 N 2 . The content of these products increased first and then decreased with the further increase of oxygen content. Comprehensively considering the influence of O 2 addition on the insulation properties and discharge decomposition characteristics, as for HV engineering application, it is recommended to add 6% O 2 in the C 4 F 7 N/N 2 gas mixture.