Mitigation of Magnetic Field Under Overhead Transmission Line

Abstract

The chapter presents an efficient way to mitigate the magnetic field resulting from the three-phase 500 kV single circuit overhead transmission line existing in Egypt, by using a passive loop conductor. The aim of this chapter is to reduce the amount of land required as right-of-way. The chapter used an accurate method for the evaluation of 50 Hz 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 conductors 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).