Modeling of Return-Stroke Current Evolution Over a Realistic Ground

Abstract

The return-stroke phase of the cloud-to-ground lightning flash is of primary concern for lightning-protection engineering. This also holds for buried cables and other sensitive devices in the soil. For evaluating the field in the soil, two approaches are employed: first, the quasi-static approach, in which a current source injects the stroke current into the soil; and second, a hybrid approach employing the “engineering model” for the channel-current evolution. In both the approches, the current injected into the soil is independent of the soil resistivity, which needs further scrutiny. The return-stroke model developed by Balaram Raysaha et al. (2011) self-consistently emulates the stroke-current evolution without any such assumptions and is, therefore, very suitable for a comprehensive assessment of the situation. However, the field-computation method employed by Balaram Raysaha et al. had to be changed to the domain-based finite-difference time-domain method for a realistic soil model. After this augmentation, the return-stroke model is employed to investigate the possible role of soil's electrical parameters on the return-stroke current evolution. It is found that for fast-rising currents of low amplitudes, the soil resistivity noticeably influences the current amplitude. Also, it is found that the soil dispersion leads to a significantly lower electric field in the soil.