A Correction to Rusck Expression for the Evaluation of Lightning-Induced Overvoltages for High-Resistivity Ground

The assessment of the indirect lightning performance of overhead distribution lines is important to enhance the reliability of power systems. This article proposes an approximate formula for the evaluation of peak values of lightning-induced voltages in presence of highly resistive grounds. The simulations have been performed using the finite-difference time-domain method, considering the various parameters, such as peak current, return-stroke velocity, and front time, as well as ground parameters, comprising resistivity and permittivity, along with the stroke location and height of the overhead line. The functional relationship between various influential parameters and lightning-induced voltages has been investigated, and, correspondingly, a correction factor is proposed in the well-known Rusck's formula. The curve-fitting technique has been adopted to propose an expression for the correction factor, and the coefficients are determined. The accuracy of the proposed formula has been validated against finite-difference time-domain simulations and the results available in the literature.