Two dimensional simulation of Post Arc phenomenon in Vacuum Interrupter with Axial Magnetic Field contacts

The Post Arc (PA) phase of Vacuum Interrupters (Vis) and the effects of dominant physical parameters of vacuum arc investigated in this paper. 2-D movement of PA plasma in the presence of Transient Recovery Voltage (TRV) is simulated in a proper Finite Element Method (FEM). The residual plasma at Current Zero (CZ) crossing is assumed in the inter-electrode space. Due to simplify the problem, a cylindrical symmetry for VI construction is considered. Continuity of mass, continuity of momentum (Navier-Stokes) and Poisson´s law are simultaneously employed to describe the physics of PA in VI. Appropriate boundary and initial conditions are considered in COMSOL Multiphysics. Furthermore, the impacts of vacuum arc parameters before CZ, like strength of Axial Magnetic Field (AMF), on PA are investigated. It is observed that stronger AMF results in lower PA current amplitude in shorter duration. Simulation is performed for two distinct TRV regimes: simplified linear TRV (1 kV/μs) and real TRV (considering peripheral circuit) and the difference between them is assessed. Simulation results indicate that faster electron movement toward the new anode, i.e. earlier initiation and expansion of ion sheath, is a consequence of TRVs with higher rate of rise of recovery voltage. It can be also concluded that the boundary between ion sheath and plasma region moves toward the new anode in non planar way which is explained by non-homogenous electric field near the electrode edges and the plasma density distribution which decreases rapidly from the center of gap through the shields.