Large Internet Facility near Los Angeles…
Clients’ Concerns: Nearby high-tension power lines were causing interference with the operation of computers in a large section of the facility near the power lines. Clients also wished to reduce EMF levels for employees.
Source of the Electromagnetic Interference: Our testing confirmed that the computer interference was indeed caused by the magnetic fields from the adjacent power lines. Our analysis also verified that the interference was not significantly due to internal sources such as electrical wiring, panels, grounding, or equipment within the building.
Solution Implemented: The most cost effective mitigation for this particular case was to install a large scale custom magnetic field cancellation system. Such systems utilize modern electronic technology to create an opposing magnetic field which “cancels out” the power line’s field. In this case, shielding would have been a relatively difficult and expensive option. For further detail, see the pictures below…
This is a picture on the roof of the building. You can see the close proximity of the power lines. Many computers in the portion of the facility near the power lines, on both first and second floors, were being affected by interference. The conduit seen here is part of the new cancellation system that we installed. This system uses a series of small “sensor coils” inside the building to detect and monitor the magnetic fields from the power lines. The system then sends a low voltage current through a specially designed loop of “cancellation wires” which encircle the problem areas. This precisely controlled current then creates an opposing magnetic field which cancels the power line field in the desired areas. (Please click image for full-sized picture.)
This is a picture of the facility taken from underneath the power lines. The large window areas made it very impractical to install shielding for the magnetic fields. And regardless of the windows, adequate shielding material for this building would have cost at least 10 times more than the cancellation system itself. One of the conduits for the system can been seen running up the outside wall in the center of this picture. While this conduit could have been installed inside the walls, the owners wanted to minimize costs, so the conduit was mounted externally and later painted to match the building. (Click image for full-sized picture.)
This is another picture on the roof. It shows more of the cancellation conduit system (in the foreground). Because of the high number of square feet needing treatment, this particular project utilized six independent cancellation systems. They were installed side by side across the length of the building to cover the entire area affectively. Each system had its own sensor, electronics, and cancellation conduit. (Click image for full-sized picture.)
In this side view, you can see one of the cancellation conduits going up the exterior wall. Also, some of the conduit is buried below the pathway, and/or hidden by landscape vegetation, so that the system is hardly noticeable. This particular system has operated for over 6 years, without a single problem, repair or adjustment needed. (Click image for full-sized picture.)
Office Building in Kansas City, Missouri…
Clients’ Concerns: Relatively high magnetic fields in the first floor offices due to a large transformer vault located directly below. Many computers were having severe interference problems. Clients also wished to reduce EMF levels to employees.
Source of the Magnetic Fields: While magnetic fields were being emitted from several sources in the transformer vault, the largest single source was from the particular way that the secondary cables were arranged in the ladder trays above the transformers.
Solution Implemented: The most cost effective mitigation for this particular case was to simply reconfigure the secondary cables above the transformers, thus reducing the EMF emissions through automatic self-cancellation. See the two pictures below…
This is a picture of the transformer vault before the fix. The offices were located directly above these transformers. The main source of the EMFs was from the large electrical cables in the ladder racks above the transformers. (Please click image for full-sized picture.)
This is a picture taken after the fix. Some of the large secondary cables above the transformers have been replaced and rerouted to provide for automatic self-cancellation. This simple modification was quite effective, yet much less costly than shielding would have been. (Click image for full-sized picture.)
Case 3. Warehouse Accounting Office in Sacramento, California…
Clients’ Concerns: An office area close to the main electrical meter and distribution panel in this large warehouse was experiencing annoying interference problems on some of the computer screens. The clients suspected that the problem might be due to electromagnetic interference (EMI) from either the main electrical panel or the nearby electrical transformer. They also wished to minimize EMF levels for employees.
Source of the Magnetic Fields: Our measurements confirmed that strong magnetic fields from the main electric meter and distribution panel in the warehouse were the chief cause of the high EMFs and computer interference in the nearby accounting office. (Please click image for a full-sized picture of the meter panel. In this picture, you can also see a layer of shielding material that we installed onto the wall directly behind the meter panel to reduce the levels.)
Solution Implemented: The most cost effective mitigation for this particular case was to install several layers of magnetic shielding alloy onto the walls near the electric meter equipment. This picture shows one layer of shielding material as it is being stapled to the existing wall inside the accounting office. The final shield design included multiple layers of 6 mil thick shielding material mounted on two walls inside the office, and another layer of shielding mounted to the wall directly behind the electrical equipment. (Please click image for a full-sized picture.)
This picture shows some of the shielding before it was covered with standard sheetrock and painted. To minimize costs, the shielding material was installed during an already planned remodel of the accounting office. (Click image for full-sized picture.)
Case 4. Electronic Manufacturing Facility in Santa Rosa, California…
Clients’ Concerns: Costly, intermittent problems with the operation of sensitive electronic hardware were being experienced by this high-tech manufacturer located north of San Francisco. Electromagnetic interference (EMI) from the building (or nearby area) was suspected, because the problem had not occurred at their previous location and began as soon as they moved to the new production facility.
Source of the Electromagnetic Interference: Mysterious interference problems were causing costly operation setbacks in their new production facility. Our initial testing showed that there were significant problems with the building’s electrical power system — serious enough to cause substantial radiated electromagnetic fields and comprise the integrity of the grounding system. For example, several amps of electrical current were found flowing through metal water pipes and building materials. Our analysis showed that the electromagnetic field problems were not significantly due to external sources such as power lines, or from the building’s electrical service entrance equipment or electrical transformers. The wiring system seemed to be the most likely cause of the interference problems.
Solution Implemented: We systematically traced and repaired a series of error conditions within the building’s electrical system. First, we initiated a very thorough and complete inspection and testing of all electrical panels, subpanels and circuits. This was done to detect any wiring errors or other problems that might cause stray electrical current (or voltage) to “leak” into the grounding system or travel improperly within the neutral wires. Either of these conditions are common causes of both radiated and conducted electromagnetic interference. Our testing found six important wiring errors, all of which were easily corrected. Six months later, the company’s production engineer confirmed that the interference problems stopped right after we repaired the building’s wiring problems.