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.