Effect of frequency-dependent soil parameters on wave propagation and transient behaviors of underground cables

This paper investigates the influence of frequency-dependent (FD) soil parameters in comparison to the constant soil (CS) parameters on wave propagations and transient characteristics of underground cables. Various FD soil models are summarized, and the calculated results of the FD soil parameters are compared with independent measured FD soil data. Longmire / Smith (LS) model is found to show the best agreement with the measured results. The frequency responses of wave propagations on underground cables are studied by the recently proposed extended transmission line (TL) approach together with the CS and the LS FD soil models. Calculated transient responses show more attenuation with a large soil resistivity at 100 Hz in comparison with those with a small soil resistivity at 100 Hz. Further, the transient voltage responses of a cross-bonded cable are compared with the transients solved by the Cable Constants and the existing FD soil routine in an EMT-type simulation tool, and a significant difference is observed.