Investigation on Shielding Method of ELF Magnetic Field Generated from Conductors

We have studied experimentally the shielding method of ELF magnetic field applied to the source of line conductors. For the single-phase line current, it appears to be difficult to achieve the effective shielding. On the other hand, for the balanced 3-phase conductors, including triangle and twisted configuration, a certain reduction of generated magnetic field was achieved by adjusting the configuration of conductors or by surrounding the conductors with cylindrical shielding materials made of ferromagnetic materials or non-ferromagnetic metals. Normalized characteristics between phase current, distance between source current and observation point, distance between phase conductors, and the pitch of twisted cable were derived. In addition, the effect of unbalanced current was also investigated.