Modelling of switching arcs at short electrode distances

Properties of the arc plasma at electrode distances below 1 mm have been studied by one-dimensional time-dependent (1D-t) fluid-Poisson model. Silver vapour is assumed to be the arc medium, as the electrodes mainly contain Ag. Pronounced voltage falls in the near-electrode regions were found. The model predicts clear thermal non-equilibrium as well as negative anode fall in case of small DC currents. For implementation in power grids simulations, a simplified arc model in form of current – voltage characteristics was derived. Predicted modelling results for electrical characteristics at various conditions have been compared with experimental results obtained for a low-voltage DC hybrid switch. A reasonable agreement between predicted and measured data was found.