Assessment of different formulations for the ground return parameters in modeling overhead lines

There is a growing concern regarding a more accurate assessment of the transient behavior of overhead lines and underground cables. Traditionally, displacement currents are neglected in the evaluation of the ground return correction terms, thus only the transmission line impedance being affected. However, if these currents are to be considered, the ground cannot be assumed as an equipotential and there are some ambiguities depending on the definition used to determine the conductors' voltages. Furthermore, given the numerical challenges associated with the infinite integrals needed to obtain the ground return parameters, it is rather common to use closed-form approximations instead. In this paper, we assess the influence that the different formulations may have in modelling two distinct overhead lines. Both frequency and time-domain results are presented and discussed. The results indicated that there are some mismatches between induced voltages calculated using the voltage formulation with quasi-TEM approximation and those using the potential formulation with closed-form approximations.