Research on the Postarc Sheath Growth Process Considering the Plasma Motion and Distribution

Abstract

In this article, the sheath growth of the vacuum circuit breaker and its initial conditions of the calculation are introduced. The images of cathode spots distribution and waveforms of postarc current under different frequencies are obtained by medium- to high-frequency current breaking experiments. The quantitative relationship of $D$ and $di/dt$ with the variation of current frequency $f$ and current amplitude $I_{m}$ is obtained by fitting the data. The reasons for the change of postarc current parameters are reasonably explained by the analysis of equivalent circuit and plasma movement process. Combined with the continuous transition model (CTM) and its initial calculation conditions, the influence of the cathode spots distribution diameter $D$ and $di/dt$ after the current zero crossing on the sheath growth is analyzed. An initial postarc plasma density calculation model which is suitable for each current frequency is proposed which makes the calculation of the sheath growth more accurate, especially when applied to medium- to high-frequency current conditions.