Earth Return Impedances of Conductor Arrangements in Multilayer Soils—Part I: Theoretical Model

The influence of earth stratification on the conductor impedances is investigated in this paper. A general solution of the electromagnetic-field equations for the case of overhead and underground transmission-line conductors of arbitrary topology and multilayer earth is presented. Generalized expressions for the self and mutual impedances of the conductors are derived. All existing approaches result from the generalized equations, when the corresponding approximations are applied. A suitable integration scheme is also proposed for the calculation of the complex integrals involved in the expressions.