Electric Field Distribution Analysis During the Very Fast Transient Process Based on 3D Full Maxwell Simulation

Most simulations of electric field distribution during the very fast transient (VFT) process are based on equivalent waveforms, which affects the analysis of the electric field. In this paper, the actual VFT process is simulated based on the 3D full Maxwell finite element method (FEM). The electric field distribution at different points is measured. To investigate the influence of the induced electric field during the VFT process, and whether high amplitude or high steepness is the main factor affecting insulation during the VFT process, the simulation results are compared with the electrostatic simulation results. The results show that the induced electric field caused by the wave process does not play an important part. The electric field distribution is hardly influenced by the induced electric field. Therefore, the threat to insulation caused by VFTO is mainly due to its high amplitude, which leads to a stronger Coulomb electric field. Besides, the wave process only leads to a 6~8% voltage amplitude increase, which is much lower than the amplitude increase due to externally generated low-frequency oscillations. Therefore, the high amplitude of VFTO is mainly caused by low-frequency oscillations, rather than the high-frequency components during the VFT process.