Calculating Mutual Ground Impedances Between Overhead and Buried Cables

Aerial and buried electric conductors often share the same right of way. When a phase-to-ground fault occurs, high transient-induced overvoltages appear from short-circuit currents to the ground. The mutual ground-loop impedances between both systems are given by the Pollaczek coupling integral that does not possess an analytic closed-form solution, and its integrand is highly oscillatory to perform a direct numerical integration. An efficient and accurate algorithmic evaluation of the Pollaczek coupling integral is presented in this paper. The obtained result is used in the numerical assessment of approximated formulas previously issued by Lucca, Wedepohl, and Comite Consultatif International Telephonique et Telegraphique.