Orono Substation Expansion - Enviromental Assessment (1)

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I electric fields generated by other common household/business sources and well below the various I state and international organization established guidelines. The maximum calculated electric field on the entire length of project,directly beneath transmission I centerline at 3.28 feet above ground is estimated to be 1.09 kV/m. This maximum calculated electric field is approximately 14 percent of the 8 kV/m guideline historically recommended by the I Minnesota Environmental Quality Board (EQB) and the Commission in other route permit proceedings and again,well below any of the national and international recognized electric field guidelines as identified in Tables 10 and 11. I Magnetic Fields Electric current passing through a conductor produces a magnetic field in the area surrounding the wire. Similar to electric fields,magnetic fields are strongest near the conductor and diminish with I distance. Magnetic fields,however,are not shielded by most common materials and easily pass through them. The magnetic field may also be called magnetic flux density and is measured in units of milligauss (mG) or microtesla (µT). I We encounter magnetic fields from every-day things such as radar and microwave towers, television and computer screens,motors, fluorescent lights,microwave ovens,cell phones, electric I blankets,house wiring and hundreds of other common electrical devices. The general wiring and appliances located in a typical home can produce an average background I magnetic field of 0.5 mG to 4 mG (EPA, 1992). A U.S.government study conducted by the EMF Research and Public Information Dissemination Program determined that most people in the United States on average are exposed to magnetic fields of 2 mG or less daily,and varies by I individual (NIEHS,2002). Table 13 summarizes the average level of magnetic fields of common appliances. Table 13: Typical Magnetic Fields (mG) of Common Appliances I Distance from Source I Source 0.5 foot 1 foot 2 feet 4 feet Baby Monitor 6 1 - - I Computer Displays 14 5 2 Fluorescent Lights 40 6 2 I Copy Machines 90 20 7 1 Microwave Ovens 200 4 10 2 I Electric Pencil Sharpeners 200 70 20 2 Vacuum Cleaner 300 60 10 1 I Can Opener 600 150 20 2 Color Televisions NA 7 2 - I Source: NIEHS,2002 Environmental Assessment I PUC Docket E002/TL-11-223 Page 34 I