Ground return effect on wave propagation parameters of overhead power cables

It is noted that the propagation properties of overhead three-phase cables are usually analyzed assuming that the pipe conductor establishes a perfect shielding between the inner conductor set and any outer conductor, i.e. the power cable is assumed to be an isolated system. The influence of a lossy ground plane in the neighborhood of the cable is examined in the present work. The propagation parameters for both approaches are compared, and significant differences are found to exist, in the zero mode, at low working frequencies. Relative errors up to 60% have been determined in the attenuation, velocity, and surge impedance. A physical interpretation of these results is presented. It is based on the imperfect screening action of the pipe which allows the magnetic field to spread outside the cable and penetrate the imperfect soil, giving rise to a higher series inductance and a smaller series resistance