Transient Analysis of Buried Cables Considering a Nodal Admittance Matrix Approach

In this paper, the transient behavior of buried bare and insulated cables is analyzed using transmission line (TL) theory. The proposed approach is based on a passive pole-residue model of the nodal admittance matrix, which can be represented as an electrical network suitable to time-domain simulations in electromagnetic transients programs. The influence of a finitely conducting soil is computed by means of Sunde's ground return impedance equation. An approximate expression is considered to represent the ground admittance. Furthermore, the frequency dependence of the electrical parameters of the soil is considered. The proposed methodology is validated by comparing the results it provides with those obtained by a popular electromagnetic transient program and a field theory approach. The results show that ignoring the ground admittance and the frequency dependence of soil parameters can lead to inaccuracies in transient studies involving buried cables, especially in the case of high-resistivity soils and transients with a wide frequency range.