Generalized Formulation of Earth-Return Impedance/Admittance and Surge Analysis on Underground Cables

A generalized formulation of earth-return impedance and admittance for underground cables is proposed based on a complete solution of Maxwell equations. The frequency responses of wave propagation characteristics are evaluated by the newly derived formulas and compared to those found from existing formulas in software used for the simulation of electromagnetic transients. Surge simulation results with the proposed formulas show more damping and smooth convergence to steady state in comparison with those with existing formulas. The proposed formulas are validated with a field test on a 110-kV cross-bonded cable. It is also shown that the MoM-So method, augmented with admittance representation, verifies the results found from the new formulas presented in this paper.