Effect of oxygen on power frequency breakdown voltage and decomposition characteristics of the C5F10O/N2/O2 gas mixture

Sulfur hexafluoride (SF6) 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 SF6 is becoming significantly critical. In recent years, C5F10O has received extensive attention as a potential alternative to SF6. In this study, a part of N2 in C5F10O/N2 was replaced by O2, and the breakdown voltages of C5F10O/N2/O2 at different oxygen concentrations under a slightly uneven electric field were tested. The dispersion of breakdown voltage and the discharge decomposition components of C5F10O/N2/O2 with different oxygen concentrations were analysed. It was found that as the oxygen concentration increased, the breakdown voltage of C5F10O/N2/O2 with 15 kPa C5F10O at 0.2 MPa increased, and the dispersion of the breakdown voltage became worse. When 0.5% O2 or more O2 was added to the C5F10O/N2 gas mixture, the carbon precipitates on the electrode surface disappeared. As the oxygen concentration continued to increase, another characteristic component, CF2O, could be detected, whereas C2F4 and C3F6 disappeared. It is believed that O2 can inhibit the formation of C2F6, C3F8, C4F10, and C3F7H. Therefore, it is recommended to use oxygen as the second buffer gas for the engineering applications of C5F10O. Moreover, the ratio of C5F10O to O2 is recommended to be 1 : 1.