Generalized Formulation and Surge Analysis on Overhead Lines: Impedance/Admittance of A Multi-Layer Earth

A generalized formulation of earth-return impedance and admittance for overhead lines above a multi-layer earth is derived. An equivalent homogeneous earth method (EHEM) and a Method of Moments - Surface Admittance Operator (MoM-SO) method with modified earth-return Green function considering an N -layer earth are also proposed. The frequency responses of wave propagation characteristics are evaluated by the newly proposed formulas and compared to those found from existing formulas in software used for the simulation of electromagnetic transients. Transient simulations performed in an electromagnetic transient (EMT) type simulation tool are also presented. It is shown that the proposed generalized formulas, the EHEM and the modified MoM-SO method, are in agreement, validating and verifying the results found in this paper.