Investigation on Magnetic Shielding for ELF Magnetic Field
from Three-Phase Electric Power Line

Abstract

Recently it is necessary to reduce ELF (Extremely Low Frequency) magnetic field, which arises from the electric power line in the building. The magnetic shielding with ferromagnetic material is effective in the reduction of ELF magnetic field from the three-phase electric power line. Then, the current of the electric power line fluctuates in proportion to use load, season and time.
Therefore, we experimentally measured the magnetic shielding effectiveness with current fluctuation. Also, we numerically calculated them using the finite element method reflected the nonlinearity of the magnetization characteristics. The magnetic material selected thin plate of the permalloy. Characteristics of single-layer shielding and multi-layer shielding were examined.
It was confirmed that the shielding effectiveness increased with the increase in the current and that it decreases from the threshold. As a result, it was proven that the shielding property was able to estimate by the finite element method analysis considering magnetization curve.