A Practical Extension of Rusck´s Formula for Maximum Lightning-Induced Voltages That Accounts for Ground Resistivity

The effects of ground resistivity (rho) on overhead line voltages induced by nearby lightning flashes to ground are reviewed and descriptions are given of experimental field data and of analytical studies of these effects. A semi-empirical extension to Rusck´s formula for maximum induced voltage to account for the effect of rho is proposed, and this involves substituting the line height (h) in the formula by an effective height h_eff=h+0.15 radicrho. Finally, its validity is assessed by means of results published by other authors