Study of the Arc Interruption Performance of SF6 Alternative Gases in Load Switch

SF ₆ gas is widely used in power equipment for its excellent arc extinguishing and insulation properties. However, SF ₆ is a strong greenhouse effect gas with a global warming potential (GWP) of 23,500 times that of CO₂. Therefore, the Kyoto Protocol signed in 1997 has included SF ₆ in one of the six greenhouse gases which are restricted for use. Nowadays, finding an environmentally friendly alternative gas for SF ₆is a hot issue in the world. The research on SF ₆ environmental alternative gas has made great progress these years. C5F₁₀O is considered the most likely gas to replace SF₆ in the near future. Although C₅F₁₀O has a good arc extinguishing property in general, the arc extinguishing mechanism of it in the load switch is not clear. Because arc extinguishing is a complex physical and chemical process involving the interaction of gas flow fields, electromagnetic fields, and ablation the nozzle materials. In this paper, by combining the computational fluid dynamics (CFD) analysis and the Mayr arc model the interruption processes for a load switch filled with 5^%C₄F₇N/CO₂ and 5^%C₅F₁₀O/CO₂ at 0.135 MPa, as well as pure SF6 and CO₂ at 0.135 MPa, are investigated. The time constant θ and arc cooling coefficient Q at the current zero point is calculated based on the Mayr equation. In the end, the critical values of the rising rate of the recovery voltage (RRRV) are obtained. These parameters are the most important issues to determine whether breaking success or not. Through the analysis of the post arc medium recovery, the arc extinguishing performance of different gas medium can be theoretically and quantitatively evaluated. It can provide a sufficient theoretical basis to enhance the arc extinguishing ability of the load switch through the CFD analysis.