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.