An improved arc model for vacuum arc regarding anode spot modes

This paper introduces an improved arc model for vacuum arcs. In this model, the impact of different high-current anode modes is considered. An existence diagram for different high-current anode modes including footpoint, anode spot type 1 and type 2 is determined using emission spectroscopy, high-speed camera, and electrical measurements. During transition from diffuse to the high-current mode the arc voltage will be affected due to high evaporation rate, which can affect dielectric recovery of vacuum interrupter. Conventional arc models cannot trace the corresponding sudden changes in the arc voltage during the transition to anode spot type 2. Therefore, different areas of discharge modes are determined based on the threshold current and gap length for AC 50 Hz and cylindrical contacts made of CuCr7525. The physical parameters of the arc, e.g. the arc temperature, contact geometry and material is considered as implicit parameters in the existence diagrams. The boundaries of the areas are used as a user-defined library in EMTP-RV for a new electric arc model. The voltage behavior of the arc can be predicted well in a larger range of peak currents by the results. The validity of the model is also investigated for AC 100 Hz and pulsed DC 10 ms.