Computer Simulation of Faulted URD Cables: Analysis and Results

A method for computing shield potentials of underground directly buried (URD) cable is presented. Earth potentials in the vicinity of the buried cable are also computed. The method utilizes a numerical solution of Laplace´s equation to account for earth currents, and a modified nodal analysis method to account for conductor and shield currents as well as inductive coupling in the underground cable system. A computer program has been developed capable of analyzing long lengths of URD cable together with existing ground rods, faults, open neutrals, feeding substation and substation grounds. The system analyzed corresponds to practical URD cable distribution systems. Extensive simulation of various URD cable systems in various soil environment has been performed and the results have been tabulated in a two-volume EPRI report.