Abstract
This paper presents a dielectric simulation approach for predicting withstand voltage of air insulated power devices. The paper gives an overview of typical evaluation procedures for the basic discharge stages including inception, streamer propagation and leader transition. For selected test arrangements, we compare the results of lightning impulse tests with simulations. The simulations utilize a new approach that combines the well-established empirical procedure with numerical computations for arbitrary geometries. We introduce a new formulation for evaluation of saturation charge density, which enables a revision of the streamer inception conditions due to surface charging and an estimation of the leader transition characteristics including the surface capacitance.