Accuracy Verification of Analytical Expressions for the Calculation of the Ground-Return Parameters of Underground Cables

Abstract:
This paper discusses the calculation of the per-unit-length parameters of underground cable systems based on analytical expressions that were recently proposed for determining the ground-return impedance and admittance required in models based on transmission line theory. It is demonstrated that wave-propagation characteristics calculated for a threephase cable system obtained with the use of these recently-proposed expressions closely reproduce those obtained with more rigorous integral expressions up to the MHz range. In addition, time-domain evaluations indicate that the use of transmission line modeling considering the investigated expressions is able to reproduce results obtained with a rigorous full-wave electromagnetic model. Given their accuracy in a wide range of frequencies, it is concluded that the investigated expressions are sufficiently accurate for the time-domain simulation of lightning-related problems.