An Improved Method for the Calculation of the Internal Impedances of Solid and Hollow Conductors With the Inclusion of Proximity Effect

We present a new method for the evaluation of the per unit length (p.u.l.) internal impedances of solid and hollow conductors. Our method is semianalytical, and takes into account the proximity effect arising from currents mutually induced by nearby conductors which, in turn, modify their internal current density distribution and, hence, their impedance. We eventually apply the developed method to the case of a three-core cable and we calculate the voltages induced in its screens by a lightning current