Influence of the Frequency Dependence of Electrical Ground Parameters and Different Formulations for the Ground Correction Terms on Field-Induced Currents and Voltages on Overhead Lines

A theoretical analysis on the influence of a lossy ground on field-induced voltages and currents on overhead lines is presented. It is shown that the frequency dependence of the ground conductivity and permittivity leads to a decrease of the amplitude of the field illuminating the line, especially in the case of a poorly conducting ground. It was also shown that often-used Sunde’s formulation to calculate the ground correction terms might underestimate the induced currents/voltages, depending on the frequency content of the exciting EM field. More complete formulations, such as that of Pettersson, are recommended when the line is illuminated by very high frequency EM fields.