Mitigation of magnetic field under Egyptian 500kV overhead transmission line

Abstract

The paper presents an efficient way to mitigate the magnetic field resulting from the three-phase 500kV single circuit high voltage transmission line existing in Egypt, by using a passive loop conductor in order to reduce the right-of-way (ROW). The paper used an accurate method for the evaluation of 50Hz magnetic field produced by overhead transmission lines. This method is based on the matrix formalism of multiconductor transmission lines (MTL). This method obtained a correct evaluation of all the currents flowing in the MTL structure, including the currents in the subconductors of each phase bundle, the currents in the ground wires, the currents in the mitigation loop, and also the earth return currents. Furthermore, the analysis also incorporates the effect of the conductor's sag between towers, and the effect of sag variation with the temperature on the calculated magnetic field. Good results have been obtained and passive loop conductor design parameters have been recommended for this system at ambient temperature (35°C).