Charge-flow and field in soil due to return-stroke

The evaluation of the electric field gradient along the air-soil interface, generally termed as the step-potential, is an important parameter of practical interest. Generally, the peak value of the step-potential is one of the primary target variables in the design of the earth termination. Two of the most popular approaches used in the literature for its evaluation are the quasi-static approach, in which a lumped current source is employed to inject the return-stroke current to the ground/grounding system and the antenna-model approach, in which a voltage source at the ground end of a monopole is employed to set up the return-stroke current. When viewed in terms of the charge dynamics and in terms of the channel current evolution, both these approaches are found to have certain limitations. This work, by employing a self-consistent return stroke model along with a full representation of the soil, intends to address the above lacunae. It is shown that the step-potential predicted are different for different models and so is the current flow patterns in the soil. Based on the same, the advantage of employing a self-consistent model for the return stroke is demonstrated.