Influence of ablated PTFE vapor entrainment on critical dielectric strength of hot SF6 gas

The influence of PTFE vapor injected into the SF6 on dielectric strength of hot gas mixture which corresponds to the dielectric recovery phase of a high voltage circuit breaker are investigated in the temperature range from 300K to 3500K. The equilibrium compositions of hot SF6/PTFE vapor mixture were determined based on Gibbs free energy minimization. Additionally, adopting full sets of improved cross sections, the critical reduced electric field strength of this derived composition was obtained by a balancing electron generation and loss modeled by the interactions between electrons and the dissociated species of hot gas evaluated by the electron energy distribution function (EEDF) derived from the Boltzmann transport equation. Results indicates that above the temperature of 2500K, the addition of PTFE vapor leads to a higher critical breakdown field which is an important result for practical applications.