Evaluation of the Step Voltages for Grounding Grids at Lightning Strikes

Flowing impulse lightning currents in the grounding grids of substations may cause an increase of the possible potentials and step voltages to few tens of kV independently from the grounding resistance. This paper suggests an approach for determination of the permissible step voltages' values in grounding installations under the effect of impulse lightning currents with a certain shape. The allowable body current was determined as an energy limit of 10J was accepted as the lowest determined value by researchers in the literature. Comparison of the obtained maximum step voltages and the values of defined permitted step voltages has been done by using a previously developed by the authors model for simulation the processes in grounding grids when the lightning currents flow in them.