Active compensation and partial shields for the power-frequency magnetic field reduction

A combined technique for the mitigation of the power frequency magnetic field due to power lines, based on the use of both active conductors and passive shields, is presented. The main idea relies upon the use of either existing conductors (guard-wires) and new conductors to be installed, generally buried cables. In the past, active shielding has been almost always applied through loops to be installed in the proximity of the area to be shielded, while in this method the return of the currents is through the ground just for the shortest possible line length. The technique, applied to both overhead lines and underground cables, may be extended to other unintentional sources of higher frequency.