JOURNAL OF MAGNETIC SHIELD CASE STUDIES

Power to the People – But Not Magnetic Fields
Case #12946

Blackouts and brownouts plagued a major Midwestern power utility during summer peak loads. The power company urgently needed to upgrade its system to eliminate these services problems. To reinforce system capacity in a neighborhood of rapid urban growth, an entire 138KV to 12KV substation had to be packed into a small lot near existing facilities. Four large step-down transformers, switchgear, inductors and capacitor banks were required.

The solution was a “high rise” substation building with four equipment levels, but a five story condominium was already standing a scant eighteen feet from the proposed substation. Concerned condo residents feared exposure to magnetic fields. To allow construction of the substation, these neighbors had to be satisfied that magnetic field emission would be kept to a minimum.

While complete elimination of magnetic field emissions from an installation such as this substation is not practical, Magnetic Shield Corporation was called in to develop effective mitigation of the emissions.

We performed a detailed magnetic field survey of the area. Because field observations and calculations confirmed that high levels of magnetic fields could be present in the condominium, there was complete commitment by the engineers from the design firm and the power company to reduce the magnetic fields.

Two layers of our shielding alloy were utilized. The first was a 0.095” thick NETIC S3-6 alloy which successfully handled the expected amount of magnetic flux. The second stage of our magnetic shielding system was 0.062” thick CO-NETIC AA alloy Perfection Annealed sheet. This alloy provides the highest permeability (affinity for magnetic field) and therefore the best attenuation of the magnetic fields. When an installation requires the use of the two different alloys, the NETIC is placed closest to the source of the interference. In this case, that was on the substation side of the shield assembly.

As a result of our shielding system combined with the distance of the substation to the condominium, the level of magnetic field emission reaching the condominium is less than 5 milliGauss at the building, so low that it would cause no effect on any electronic equipment. As a result, condo residents have reported no magnetic field problems..