Evaluation of Lightning-Induced Voltages over Lossy Ground with Frequency-dependent Soil Parameters

This paper presents a comprehensive evaluation of the effect of frequency-dependent soil parameters on lightning-induced voltages by means of Visacro-Alipio formulae implemented in the Hybrid Electromagnetic Model (HEM). The results indicated this effect differently affects induced voltages along the overhead line. For high resistivity soils, at line center, the frequency dependence effect of soil parameters contributes to reduce the amplitude of induced voltages, although at line extremity, this effect promotes the increase of the resulting amplitude, considering a 50-m distant stroke from line center. Sensitivity analyses show this behavior is related to effect of frequency-dependent soil parameters on the horizontal component of the electric field. The results also show that, for the critical condition of the lightning performance of the line, the frequency-dependence effect of soil parameters leads to a decrease of the expected flashover rate.