Stray voltage

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"Stray voltage" is a term commonly used throughout the electric utility industry to describe when infrastructure devices, such as lamp posts, manholes, gratings and junction boxes become unintentionally charged with electricity. The cause of this unintended electric leakage is due to a variety of conditions including cracked insulation, frost heaving, expansion and contraction of wiring, physical damage to the lines and so on. In major metropolitan areas, such as New York City, "stray voltage issues" have become a major concern. In 2005 a woman named Jodie S. Lane was killed in New York City after she was electrocuted after stepping on an electrified manhole cover.[1] As a result, Con Edison, the electric provider for much of the north eastern part of the United States, has been testing real time, on-site, stray voltage warning concept, that was patented by the Electrified Cover Safeguard. Nevertheless, each year there are a number of stray voltage injuries to people and to pets.

The term "stray voltage" is also used, primarily in rural areas, to describe the gradient of electrical potential with respect to soil surface location associated with single-wire earth return electricity distribution systems used in some rural locations, particularly in the USA. Campaigners claim this can lead to animals receiving a mild shock from grounded objects, similar to that produced by an electric fence. The term is also applied to a disparate range of electrical and magnetic phenomena more accurately known as EMF (Electric and Magnetic Fields). The physiological effects of these phenomena are entirely different however.

Some claim that stray voltage can have other, more harmful effects on animal health and productivity, and certain American dairy farmers have attempted to claim compensation for damage to yields or stock allegedly caused by it.

Douglas J. Reinemann, Ph.D., Professor of Biological Systems Engineering at University of Wisconsin-Madison, reported in 2003 [1] that an expert study conducted by the State of Minnesota found an overwhelming majority of diary farmers did not regard 'stray voltage' as a danger to their animals. Several field studies have found that the electrical and magnetic fields commonly found on dairy farms are well below the strength required to produce any biological effects. Even when a low level electric current was directly applied to cows, theoretically producing small internal electric fields, no ill effects were discerned.

The report to the State of Minnesota which Dr. Reinemann quoted produced 3 main findings:

  • "We have not found credible scientific evidence to verify the specific claim that currents in the earth or associated electrical parameters such as voltages, magnetic fields and electric fields, are causes of poor health and milk production in dairy herds."
  • "At the present time, there is no basis for altering the PUC-approved standards by which electric utilities distribute power onto or in the vicinity of individual dairy farms."
  • "There are many well-documented non-electrical factors that are known and accepted by the scientific community, and by most farmers as well, to cause dairy cow health and production problems. Among the most noteworthy factors are poor nutrition, poor cow comfort and hygiene, and low or no use of vaccinations and related preventive veterinary practices. These factors should always be addressed by those who want to improve performance of dairy herds."

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[edit] Stray voltage in Wisconsin

In 2003, the Wisconsin Supreme Court upheld a judgement of $1.2 million against the Wisconsin electrical utility WEPCO in Hoffman v. Wisconsin Electric Power Company. The Hoffman family, dairy farmers near New London, had sued WEPCO after several years of declining production. WEPCO had measured stray voltage on the farm below one milliampere, the "level of concern" set by the Wisconsin Public Service Commission, but the court ruled on procedural grounds that the utility could be found negligent under common law even though they met the state standard. The Hoffmans had presented, the court said, a viable alternative theory that stray voltage had caused them economic harm.[2]

Subsequently, a bill was introduced in the Wisconsin legislature to create an "electrical bill of rights", setting a deadline for utilities to eliminate stray voltage and a 30-day window for responding to reports.[3]

[edit] Stray voltage in New York City

Consolidated Edison has had frequent incidents of stray voltage. [2] including the death of Jodie S. Lane in 2004, while walking her dog in Manhattan. A recent patented invention described on ABC-TV called the Electrified Cover Safeguard may minimize stray voltage accidents since it provides for real time on site warning for street lights, manholes and utility boxes.

[edit] References

  1. ^ Con Ed Finds 1,214 Stray Voltage Sites in One Year - New York Times
  2. ^ "Wisconsin Supreme Court Upholds $1.2 Million Stray Voltage Judgment", Boardman Municipal Law Newsletter, August 2003. Retrieved on 2007-05-30. 
  3. ^ Tom Sheehan. "Lawmaker to tackle stray voltage", Wisconsin State Journal, August 17, 2003. Retrieved on 2007-05-30. 

[edit] External links