An Approximate Formula for the Peak Value of Lightning-Induced Voltages in Overhead Lines

An approximate formula is proposed to estimate the peak value of lightning induced voltages in an infinite line, considering the soil resistivity. The formula is derived from results of a computer code for lightning induced voltage calculation. The code is based on Rusck´s formulation for the vertical electric field, for a perfect conducting earth, and the formulation for the horizontal electric field for finitely conducting earth proposed by Barbosa and Paulino. The electromagnetic field coupling with the line is carried out using the model proposed by Agrawal. The results are compared with experimental data from Barker for validation purposes. The paper also presents an extension of the methodology proposed in IEEE Std.1410 Guide to include the effect of the soil finite conductivity in the assessment of the lightning performance of distribution lines due to nearby strikes. The annual indirect lightning induced voltage flashover rates obtained with IEEE Std. 1410 method are compared with the approximate formula results.