Efficient Evaluation of Earth Return Impedances of Arbitrary Conductor Arrangements With a Horizontally Multilayered Soil

The evaluation of the earth return mutual impedance of arbitrary conductor arrangements with a horizontally multilayered nonmagnetic soil is of great significance when the electromagnetic compatibility is concerned. To evaluate the earth return impedance accurately and efficiently, a semianalytical approach is proposed in this paper. With the proposed approach, the expression of the earth return impedance, which includes a complex highly oscillatory integrand, is divided into two parts, i.e., the definite and the tail integral. The definite integral is evaluated by using the moment technique and the tail integral is evaluated by using the exponential integrals with an asymptotic integrand. The numerical examples show that the proposed algorithm can evaluate the earth return impedance with various parameters and arbitrary conductor arrangements accurately and efficiently and the required computational time of the proposed approach is almost independent of the geometric and electric parameters.

I. Introduction

The evaluation of the earth return impedance of the horizontally arranged parallel conductors is of great significance when the electromagnetic coupling between the earth return circuits is concerned. The earth return impedance is closely related to the induced eddy current in the soil. Generally speaking, the soil can be represented by horizontally stratified multilayer models, which has a great impact the distribution of the induced eddy current. Consequently, it is necessary to take the soil structure into account when evaluating the return impedance.