The influence of ground wires on the resistance and reactance of high voltage overhead power lines

In this paper, the influence of ground wires on the resistance and reactance (longitudinal impedance) of high voltage overhead power lines (OPLs) is considered and the method for its calculation is described in detail. This is important considering the power flow calculation and the design of the protection system of OPLs, especially those which use distance relays. In addition to symmetric, asymmetric operating conditions of OPLs are also studied, for the analysis of which symmetric components are used. Specifically, this meant the calculation of longitudinal impedances of OPL for positive, negative and zero sequences in each considered case. Special attention is paid to the symmetric system with zero sequences, because the influence of ground wires on the change of longitudinal impedance of OPLs is the greatest in that case. The cases of OPLs with one (110 kV OPL) and two (400 kV OPL) ground wires are considered, using the values o f their parameters that can be found in real systems. Values of longitudinal impedances, obtained with and without ground wires influence or the influence of some of their parameters, are compared, based on which appropriate conclusion is made.