The effects of SF6-Cu mixture on the arc characteristics in a medium voltage puffer gas circuit breaker due to variation of thermodynamic properties and transport coefficients

摘要

In a gas circuit breaker, metal vapor resulting from electrode erosion is injected into the arc plasma. The arc then burns in a mixture of SF_6 and electrode vapor, which has properties significantly different from those of pure SF_6. Thermodynamic properties and transport coefficients of thermal plasmas formed in SF_6-copper vapor mixtures change as a function of temperature and pressure. The property that is mostly affected by the presence of copper is electrical conductivity, which is important in magnetohydrodynamic (MHD) analysis. In this study, the transport coefficients of SF_6 in the presence of 10 percent copper are considered as the basis of MHD simulation. Comparisons are made between the results during arc formation for pure SF_6 and SF_6-Cu mixture in a medium voltage (MV) circuit breaker. According to the transport coefficients influenced by the SF_6-Cu mixture, the distribution of the electric potential, temperature, electromagnetic force density and current density of the arc column are presented and discussed. Also, the arc stability and pinch effect near current zero with 3-D simulation are investigated, which is advantageous to improving the efficiency of arc plasma simulation.