The influence of nonhomogeneous earth on the inductive interference caused to telecommunication cables by nearby AC electric traction lines

This work investigates the inductive interference caused by ac electric traction lines to nearby buried telecommunication cables, in the presence of a nonhomogeneous earth. The two dimensional, quasi stationary electromagnetic field diffusion equation has been numerically solved by using the Finite Element Method (FEM), in a system involving an ac electric traction line of the Greek Railways Organization and a buried cable of the Greek Telecommunications Organization. Using FEM results, magnetic vector potential in the cross-section of the examined system, as well as the longitudinal electromotive force induced in the circuit formed by the telecommunication cable and earth, are calculated. A rigorous parametric analysis concerning various nonhomogeneous earth models has shown a significant influence of the depth and resistivity of the first earth layer, as well as of the resistivities of the different earth layers, on the electromagnetic field and on the inductive interference caused to the buried telecommunication cable.