Effect of oxygen on power frequency breakdown voltage and decomposition characteristics of the C 5 F 10 O/N 2 /O 2 gas mixture.

Sulfur hexafluoride (SF 6 ) is widely used in the power industry because of its excellent insulation and arc extinguishing performance; however, as the global environment is deteriorating, the need to replace SF 6 is becoming significantly critical. In recent years, C 5 F 10 O has received extensive attention as a potential alternative to SF 6 . In this study, a part of N 2 in C 5 F 10 O/N 2 was replaced by O 2 , and the breakdown voltages of C 5 F 10 O/N 2 /O 2 at different oxygen concentrations under a slightly uneven electric field were tested. The dispersion of breakdown voltage and the discharge decomposition components of C 5 F 10 O/N 2 /O 2 with different oxygen concentrations were analysed. It was found that as the oxygen concentration increased, the breakdown voltage of C 5 F 10 O/N 2 /O 2 with 15 kPa C 5 F 10 O at 0.2 MPa increased, and the dispersion of the breakdown voltage became worse. When 0.5% O 2 or more O 2 was added to the C 5 F 10 O/N 2 gas mixture, the carbon precipitates on the electrode surface disappeared. As the oxygen concentration continued to increase, another characteristic component, CF 2 O, could be detected, whereas C 2 F 4 and C 3 F 6 disappeared. It is believed that O 2 can inhibit the formation of C 2 F 6 , C 3 F 8 , C 4 F 10 , and C 3 F 7 H. Therefore, it is recommended to use oxygen as the second buffer gas for the engineering applications of C 5 F 10 O. Moreover, the ratio of C 5 F 10 O to O 2 is recommended to be 1 : 1.