The Influence of Metallic and Plastic Vapors on Dielectric Breakdown for Low-Voltage Circuit Breaker after Current-Zero

The effects of metallic and plastic vapors on dielectric breakdown strength at atmospheric pressure after current-zero for low-voltage circuit breaker (LVCB) applications have been investigated. Dielectric breakdown is characterized by a positive value of net ionization coefficient, which is the difference between ionization and attachment coefficients. In this paper, preliminary results are presented for the case where the metallic electrode is composed of copper while the ablating plastic wall material is polyamide 6/6 (PA-66). The effects of vibrationally-excited diatomic species and electronically-excited monatomic species on breakdown strength are also presented. The excited species are observed to lower the breakdown strength. It is expected that the current approach will provide quantitative comparisons between different metallic and plastic vapor combinations observed in realistic LVCBs and the numerical results will subsequently be utilized for comparisons with available experimental data. This approach is the first step towards addressing realistic nonequilibrium conditions prevailing in an LVCB after current-zero and the results will be a valuable tool for suggesting improvements in dielectric interruption ability of LVCBs.