Opinion On The Impact Of High -Voltage Power Lines On Communication Services
This consultant was hired by an attorney representing an owner of a parcel planned for development of an upscale subdivision. Local utility company had received a permission from the city to build there a three-phase 120-kV ac power line. The owner claimed that the line would significantly reduce the value of the property. He was preparing to sue the utility company for that loss, demanding an appropriate compensation. The attorney and his client wanted an objective opinion whether the claims had a technical basis.
According to the owner, the property value reduction would be caused mostly by the expected interference of the electromagnetic field generated by currents in the power line with the local communication services, specifically the cell-phone networks and wireless Internet. The interference would likely discourage prospective homebuyers.
Based on numerous sources and his professional expertise, the consultant did not find any conclusive argument that high-voltage power lines can interfere with cell phone communications or wireless Internet services. On the contrary, the modern digital broadband technologies make cell phones and wireless Internet highly impervious to external disturbances. The following facts were invoked :
- The 60-Hz electromagnetic waves radiated by the power line are weak because of the inherent cancellation of waves generated by individual phase currents.
- For a power line acting as an effective antenna for 60-Hz waves, it would have to be 2,500 km long.
- Harmonic pollution of the national grid may result in electromagnetic interference within the frequency spectrum up to 1 MHz. Thus, a "static" can be heard on a car radio when passing a power line as the AM stations operate in the general area of that frequency. However, the cell-phone networks utilize narrow bands of the frequency spectrum near 0.9 GHz and 1.9 GHz. Respective values for the wireless Internet are 2.4 GHz and 5.8 GHz. Thus, the noise generated by the power line occupies a place in the frequency spectrum that is extremely distant from spectral locations of the said communication services.
- Inductance of the wires in the power line have the low-pass filtering effect on currents, drastically reducing those of high-frequency content.
- In contrast to the radio, today's cell-phone and wireless Internet services are provided in the digital rather than analog format, which greatly reduced the vulnerability to external interferences.
Arguably, the strongest argument for the claim of lack of interference of power lines with modern communication systems is the idea of broadband power line (BPL). In the words of James Stenger in the Broadband Power Line Tutorial, "Broadband power line (BPL) is the term coined by the FCC (Federal Communication Commission) for new modems (BPL modems) used to deliver IP (Internet provider) based broadband services on electric power lines. On April 23, 2003, the FCC adopted a Notice of Inquiry (NOI), expressing enthusiasm about the potential of the BPL technology to enable electric power lines to function as a third wire into the home, and create competition with the copper telephone line and cable television coaxial cable line."
On the other hand, several studies have unequivocally shown likelihood of depreciation of land values due to proximity of a new power line. Various human factors, such as concern of possible health effects or unsightliness of the line, play a role in such depreciation. It has been estimated that the potential reduction in sale price for a single-family homes may reach as much as 14%.
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|Resume of FKH
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