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Product Abstract

Magnetic Field Shielding Design Guide

Product ID:TR-109271
Date Published:23-Dec-1997
Pages:156
Sector Name:Environment
Document Type:Technical Results
Price:No Charge

This Product is publicly available

   9.88 MB - Adobe PDF (.pdf)

Abstract
Magnetic fields from power lines and other electrical facilities can interfere with sensitive electronic equipment such as computer monitors, electron microscopes, medical diagnostic and monitoring equipment, and air traffic control displays. Appropriate shield design to reduce magnetic field strength in an area of interest requires identification of the sources, selection of proper shielding materials and design and installation of the actual shield. This report takes the reader step-by-step through this process.

Background

Research on 60-Hz magnetic field shielding was originally started to provide options for reducing magnetic field strength near electrical facilities when health concerns arose. Recently, however, interference issues between magnetic fields and sensitive electronic equipment have become more prevalent. The concern over adverse health effects of 60-Hz magnetic fields resulted in research to develop options that could be used to reduce field strength adjacent to power lines and other electrical facilities. One important area of this research dealt with shielding with materials. Although much as been learned over the years about shielding rooms and equipment from radio frequency electromagnetic fields, little was known about how to design effective shields for power frequency magnetic fields. Traditional methods for shielding power frequency magnetic fields were both very expensive and, in many cases, marginally effective. Research has shown that the only widely used shielding material for 60-Hz magnetic fields was an expensive, high-permeability steel-nickel alloy called mumetal.

Objective

To prepare a practical guide for designing 60-Hz magnetic field shields incorporating recent research results to aid engineers and technicians assigned this task.

Approach

Investigators took results of research on magnetic field shielding and developed a practical guide for designing shielding structures. Four basic ingredients were included: information on source identification, data on material properties needed to design a proper shield, analytical techniques and design calculations needed to specify shield performance, and installation details and economic considerations. Research showed that copper sheeting commonly used for roofing could be used along with sheet steel to make an effective and economic shield. Tests and experiments along with the design of several shields used in actual practice formed the basis for this guide.

Results

This Guide represents the end result of extensive research that has added new knowledge to our understanding of shielding mechanism and material properties. Information on sources, instruments, material properties, and design techniques are described. Researchers provide examples of practical shield designs and methods for verifying shield performance. Offering a new approach, the techniques documented in the report for shielding 60-Hz magnetic fields represent a new branch of electrical engineering not previously included in college courses or text books. The research results, contrary to common belief, reveal shields made from conductive materials such as copper and aluminum are very effective in shielding 60-Hz magnetic fields from electric power facilities. As to cost, overall results provide savings over previously used shield construction.

EPRI Perspective

Production of this Magnetic Field Shielding Design Guide represents a major accomplishment in EPRI's Magnetic Field Management efforts. Techniques for evaluating edge effects, shield thickness, joints and other important features of the shield are now available. The new knowledge that has been gained from the research on shielding with materials can now be used to produce both effective shields and economic savings over traditional methods. This design guide should be a valuable source of information for utility engineers when electromagnetic interference problems arise.

Program
Program 60   Electric and Magnetic Fields and Radio-Frequency Health Assessment and Safety
Keywords
  • Magnetic Fields
  • Currents
  • Electromagnetic Fields
  • Electric Fields
  • Shielding
  • Magnetic Shielding
Report
TR-109271
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