A new general estimation curve for predicting the impulse impedance of concentrated earth electrodes

This is a further development of the experimental curve published by A.V. Korsuntsev (see Elektrichestvo, no.5, p.31-5 (1958)). The use of this curve does not require any knowledge of the critical soil ionization constant. The characteristic dimension of an electrode has been redefined to give a good resolution between two-dimensional and three-dimensional electrode geometries. The curve predicts the impedance approximately 6 mu s after the onset of the impulse, which is representative of the impedance of electrodes at the time of the peak lightning current of first strokes.