Three-dimensional MHD simulation of arc in 126 kV vacuum circuit breaker considering active anode

In vacuum circuit breakers, the anodes often become active with the heating of high current constricted arc and generate secondary plasma, which has a negative impact on interruption. The axial magnetic field (AMF) can effectively suppress the constriction of vacuum arc and improve the breaking capacity. In this paper, based on the three-dimensional (3D) magnetohydrodynamic (MHD) model, which can consider the actual magnetic field, the vacuum arc in the circuit breaker with the cup-shaped axial magnetic alloy electrodes is simulated. In the simulation, the anode no longer only receives plasma passively, but generates secondary plasma. Moreover, the ionization and recombination processes between different kinds of components, including atoms and ions of different species, are considered. The cases of different opening distance and different kinds of AMF are simulated to study their effects on circuit breaker. The simulation results show that the six slots and four slots cup-shaped AMF contacts have similar ability to suppress arc contraction. And the arc constricts more obvious with the increase of the opening distance. The simulation results in this paper are consistent with the experimental results.