Effect of oxygen on power frequency breakdown voltage and decomposition characteristics of the CFO/N/O gas mixture.

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