PTFE vapor has an important influence on the breaking characteristics of SF₆ circuit breaker. Therefore, based on the Gibbs free energy minimization method, the local thermodynamic equilibrium (LTE) composition of SF₆-PTFE-Cu gas mixtures at different temperatures is obtained. We calculated the thermodynamic properties and transport coefficients of SF₆-PTFE-Cu gas mixtures in the temperature range of 300K ~ 30000k and the pressure range of 0.1-0.8MPa. Different PTFE, copper proportions and different gas pressures have certain influence on the thermodynamic properties and transport coefficient of the gas mixtures. It can be seen that the addition of PTFE has a great influence on these physical parameters. The addition of a small amount of copper will not lead to obvious changes in properties. However, when the mole fraction of copper exceeds 10%, the thermodynamic properties and transport coefficients will change significantly. Increasing the gas pressure will increase the transmission coefficient, especially in the high temperature range. The calculated results provide necessary data for further study of plasma behavior by using MHD arc model.

thermodynamic properties,transport coefficients,SF6-PTFE-Cu gas mixtures,LTE,high-voltage circuit breakers