Coupling model for time-domain analysis of nonparallel overhead wires and buried conductors in the presence of lossy ground

Abstract

Buried conductors crossing paths with overhead transmission lines is a common occurrence. Interference caused by overhead lines has been found capable of affecting the safe, sustainable operation of the buried conductors. Such occurrences introduce an electromagnetic problem of a nonparallel structure with conductors present in both air and ground half-spaces. Electromagnetic transient (EMT) simulations of such structures are vital in predicting the behaviour of modern power networks. This paper develops a novel EMT compatible time-domain model for nonparallel overhead wires and conductors that are buried in a frequency-dependent lossy (finitely-conducting) ground. Analytical expressions are derived for the per-unit-length (PUL) impedance and admittance matrices based on thin-wire electromagnetic scattering theory. The closed-form formulations derived in this work can be easily incorporated in an EMT simulator to calculate the coupling effect between nonparallel overhead lines and buried conductors. The validity of the proposed approach is examined for various values of the ground conductivity, the radius of the buried conductor, the crossing angle, and burial depth of the conductor by comparing with results with those obtained using a full-wave approach. A case study on the induced voltage in buried conductors due to typical lightning transients in overhead lines has also been performed. • A novel closed-form formulation has been obtained for the mutual coupling of a nonparallel overhead and buried conductors. • Results obtained using the proposed model has been compared with those calculated using a commercial full-wave solver. • Case studies on the induced voltage in buried conductors due to typical lightning and switching transients in overhead lines have also been performed. • Results indicate that hazardous voltages might be induced in buried conductors at such occurrences.