Lightning electromagnetic environments of substation considering soil ionization around grounding systems

A circuit model with lumped time-variable parameter is proposed to calculate the transient characteristic of a grounding system under lightning current, which takes into consideration the dynamic and nonlinear effect of soil ionization around the ground electrode. The ionization phenomena in the soil are simulated by means of time-variable parameters under appropriate conditions. The influences of soil parameters, location of feed point, and shape of the lightning Impulse current on the transient characteristic of grounding grids are discussed. The generated electromagnetic fields in the substation are analyzed by using electrical dipole theory and image theory when the lightning current flows into the grounding system. The influence of soil ionization on the electromagnetic fields is presented.