FMS Publications

Pre-Emptive Field Mitigation of ELF Magnetic Fields During a Commercial Building Power Upgrade

THE PROBLEM:

Power or extremely low frequency (ELF) magnetic field mitigation measures in existing commercial buildings, intended to ameliorate electronic equipment interference or health concerns, can be costly and disruptive. They are also often ineffectual. In part, this is due to the fact that the design and construction of electrical systems in most commercial buildings, within the context of existing mechanical and architectural features, are not conducive to the use of traditional magnetic field management techniques.

Moreover, concerns about elevated magnetic field conditions frequently surface at exactly the moment that recent renovation or building improvements have been completed. Unfortunately, at a time when all parties involved in a building renovation should be enjoying the fruits of their efforts, it is often discovered that a magnetic field problem is present which threatens to severely strain the relationships between the building owner, tenant and property manager.

Ideally, commercial buildings should be constructed, and improvements to existing buildings implemented, with no- or low-cost design features that would minimize problems arising from areas with elevated ELF magnetic field levels. Unfortunately, and for numerous reasons, this is rarely the case.

OBJECTIVE:

It is intuitively obvious that measures to mitigate elevated magnetic field concerns in a commercial building are best considered and are most cost effective when implemented as an integral part of the design, engineering and construction process. However, very little published data exists which would substantiate this assumption.

Clearly, comparisons between and among various sets of data are inherently difficult. In addition to inequities between various labor markets, real estate markets and local construction regulations, the selection of methods and materials will in large measure be determined by the mitigation contractor.

The purpose of this study is to initiate the collection of facts and data to test this assumption, from a single contractor, beginning with an initial project involving a sizable electrical system upgrade. It is assumed that data from this and future projects will substantiate the assumption that ELF mitigation measures are most effective and cost efficient when addressed during building design and construction.

METHOD:

In this case study, the ownership and management of a large commercial office building planned to substantially increase the capacity of the building's power facilities infrastructure; both to support new tenants telecommunication and computer equipment and to provide for future growth. Space and access restrictions in the building's basement forced a decision to locate the new utility transformer and distribution equipment in an existing street level retail tenant space, with tenant spaces on all adjacent sides and a substantial "anchor" professional tenant occupying a large area immediately above the planned street level transformer vault location. Computer simulations confirmed that elevated ELF magnetic field levels were likely to exist in all of the adjacent tenant areas after installation of the new electrical facilities. Existing tenants immediately expressed concerns about equipment interference and potential health problems.

Prior to construction of the new transformer vault, a range of ELF Magnetic field reduction measures were developed to mitigate the potential for elevated magnetic field levels in adjacent tenant areas. Three principal mitigation plans were identified.

1.  
   1. Change the planned location of a 5000 amp transformer bus duct from the ceiling area of the vault (immediately beneath the second floor tenant) to a path near the floor of the vault, just under a 3 foot steel equipment platform.
   2. Installation of a shielding scheme beneath, above and on walls adjacent to the transformer.
   3. Install additional magnetic field shielding on portions of the vault and switch equipment walls. All mitigation measures to be implemented during the construction process.
2. Delay a decision until after the facilities were installed and only then, if elevated magnetic field levels ultimately proved unacceptable in adjacent tenant areas, install magnetic field shielding in the transformer vault and switch equipment room as in No. 1. This plan would necessitate the temporary removal of components (transformer, platform, cabinets, etc) from the vault and switch equipment room to permit installation. An extended power outage would also be required. It is also likely that in some instances, due to restrictions, shielding would have to be installed in tenant areas rather than in the vault or switch equipment rooms.
3. Installation after construction of the power upgrade facilities and of ELF magnetic field shielding in all of the necessary adjacent tenant spaces. This would require considerable dislocation and disruption, as work areas would have to be temporarily vacated and certain tenant improvements (partitions, wall and floor coverings, etc) removed to permit installation of shielding of floor and wall surfaces.

All of the above options were presented to the decision makers, along with estimated costs. ELF magnetic field mitigation measures as identified in No. 1, were implemented during the design and construction sequence of the new power upgrade. Time and costs directly associated with these measures were documented and compared with estimates for the other two mitigation plans (both based on implementation after construction of the new power upgrade facilities).

ELF magnetic field measurements were taken before and after energizing the new power upgrade equipment and results were compared to projections as well as the base levels prior to upgrade. Costs were estimated for the other remediation recommendations and compared to actual costs for implementation of mitigation measures during construction.

RESULTS:

Magnetic field measurements were taken at points identical to those of the initial surveys, in locations both adjacent to the electrical facilities and within spaces above the facilities. Measurements were consistent with test procedures and techniques described in ANSI/IEEE Standard 644, IEEE Recommended Practices for Measurement of Electric and Magnetic Fields from AC Power Lines. Inasmuch as binding assurances were extended from the management and owners to the tenants, the tenants were present during the measurements and confirmed the results.

ELF magnetic field levels subsequent to the power upgrade were actually below the pre-upgrade values, suggesting that the benefit of the new shielding installation, in terms of field reduction in occupied spaces, was measurably greater than the reduction due to distance from the prior, much smaller, electrical system components. Estimated costs for the alternative mitigation measures which would be required for equivalent performance were approximately 300% greater.

CONCLUSION:

Data and facts gathered during this first demonstration project begins to substantiate the assumption that measures to reduce or manage, elevated ELF magnetic field levels which may exist in a new building construction or as a result of building refurbishment or expansion, are most effective and cost efficient if implemented as an integral part of the construction process. It also suggests that it would be useful to examine options at different, multiple points in the construction process. Further, it will be important to assemble a wide range of actual projects at various levels of difficulty in order to substantiate cost-savings claims for any given project and those costs will need to be compared to the value of such measures in order to justify mitigation. Of particular value will be the experience and comparisons from a range of projects from various locations throughout the United States, which will allow for an examination of the effects of markets and labor supply. These will, we anticipate, display a variation in comparative benefits.