Computation model for ground potential and current distribution in ground impedance measurements at high-voltage towers

In this paper, a numerical model is developed to determine the earth impedance of transmission towers, which can incorporate the effect of the variations of the tower resistances along the line, the end effect of the terminating substation and the effect of the auxiliary current electrode. The model is based on the computation of the potential at the test tower and the potential at any point on the ground surface, including the contributions from all the towers. The distribution of the test current between the earth wire and towers is computed by a numerical procedure which solves the matrix equations of a circuit model of the transmission line earthing system. The earth impedance curves computed with this model are in good agreement with those obtained from a geometrical model of the line earthing system and obtained using commercially-available software.