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

Abstract

SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> gas is widely used in power equipment for its excellent arc extinguishing and insulation properties. However, SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> is a strong greenhouse effect gas with a global warming potential (GWP) of 23,500 times that of CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . Therefore, the Kyoto Protocol signed in 1997 has included SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> in one of the six greenhouse gases which are restricted for use. Nowadays, finding an environmentally friendly alternative gas for SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> is a hot issue in the world. The research on SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> environmental alternative gas has made great progress these years. C5F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> O is considered the most likely gas to replace SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> in the near future. Although C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> O 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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">%</sup> C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> N/CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and 5 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">%</sup> C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> O/CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> at 0.135 MPa, as well as pure SF6 and CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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.