Simulation of a Grid Multi-Layer Shield to Reduce the Magnetic Field of Power Lines

Abstract

Seeing the harmful effects of the magnetic field on human health, the task of reducing the magnetic flux density in places of people long-term stays near power lines is actual. One of the ways to solve this problem is a passive shielding.Analyze of shielding efficiency was performed by computer simulation using COMSOL Multiphysics software. It was created a 2D model of a three-phase 330 kV overhead power transmission line and the research area, which is a conventional residential building located outside the security zone.The magnetic field was simulated and the value of magnetic flux density in the research area was determined for cases of using a passive grid electromagnetic screen of different configurations. The efficiency comparison of different shields was performed qualitatively on the color and contour maps of the magnetic flux density distribution in the research area and quantitatively on the average value of the shielding factor.The efficiency of a single layer vertical shield, located on the building wall closest to the power line, and a horizontal shield, located at the average height of the building, were compared. It is shown that with the same metal content (the same diameter of the shield conductors and the same number of them) the vertical shield is more efficient than the horizontal, but it also cannot always provide a safe level of magnetic flux density.The configuration of the multilayer shield, which can be placed in overlapping between floors of the building, is presented. It is shown that with the same metal content such shield can provide better reducing of the magnetic field than a single-layer, and it is able, under the same conditions, to decrease the magnetic flux density to a safe level. But this configuration has one disadvantage. In the part of the building closer to the power line (approximately 4 m from the wall) the value of magnetic flux density exceeds the safe level. It is possible to reduce the width of such zone due to a denser placement of shield conductors. It was also found that the placement of the shield horizontal layers on each floor is more effective, i.e. as evenly as possible over the research area.In addition, a research the dependence of the shielding factor of the multilayer shield on the conductor’s diameter and the distance between them. It is shown that such shield allows reducing the average value of magnetic flux density in the research area hundreds of times, although with a fairly large metal content.