3D hybrid simulation of postarc sheath expansion with nonuniform residual plasmas

To optimize the performance of vacuum circuit breakers, it is critical to gain a comprehensive understanding of the intricate physical processes that occur during vacuum interruptions. One of these processes, postarc sheath expansion is of particular importance for dielectric recovery. Previous simulation studies have examined sheath expansion by assuming uniform residual plasma at current zero. However, this approach deviates from physical realism because the discreteness in the cathode spot typically causes a nonuniform plasma distribution. This distribution cannot be analyzed by previous 1D or 2D models. To address this deficiency, this paper presents a 3D hybrid simulation model that comprehensively considers the simulation of postarc sheath expansion with nonuniform residual plasma at current zero. The model differentiates between the treatment of ions and electrons to achieve an optimal balance between computational accuracy and efficiency. The model captures the inherent nonuniformity of the plasma distribution through 3D modeling. A comparative analysis was conducted on several factors that influence the sheath expansion rate, including plasma density, transient recovery voltage rate, and ion drift velocity. The study focused on the impact of nonuniformity in the residual plasma distribution. It was demonstrated that this nonuniformity can impede the overall sheath expansion and result in the local enhancement of the electric field. The simulation aims to study the postarc sheath expansion and provide insight into the underlying physical mechanisms that govern this complex process.