What Do We Know About Stray Voltage?
You may have read or heard confusing or conflicting opinions on the
effects of “stray voltage” or other forms of electrical exposure
on cows. I am aware that some people are very concerned about the possible
effects of electricity on their cows and themselves. Agencies in several
states have asked me to investigate these concerns. As a researcher
and an educator, it is my duty to inform the public of the results of
these studies. I would like to present to you a brief summary of what
the research says.
The short answer is that animals will be affected if voltage and current
exposure levels get high enough, however there is a threshold level
below which no harm will occur. Studies by hundreds of independent researchers
in many countries give us a very good understanding of the way that
electricity affects living organisms and the level of voltage and current
exposure that cause problems to cows. Research summaries can be found
at www.mrec.org and www.uwex.edu/uwmril.
Here are some of the notable findings.
- The first study of stray voltage published in New Zealand in 1962
concluded that three volts (60 Hz rms) would be a likely minimum level
for adverse effects on cows.
- A review by 15 scientists published by the USDA in 1991 concluded
that exposure levels should kept below two to four volts (60 Hz rms)
to prevent adverse responses.
- Research in the past 10 years has shown that high frequency events
require much higher voltage and current exposure levels to elicit
the same response as 60 Hz voltage and current.
- Minnesota commissioned a four-year, $4 million study by a team of
eight national experts who concluded “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.”
- Michigan’s Attorney General investigated concerns about ‘ground
currents’ created by utility grounding. An administrative law
judge ruled that the complaint be dismissed because there was no evidence
that problems resulted from grounding electrical distribution systems.
Wisconsin regulators established one volt in cow contact locations
(two milliamps of 60 Hz current flowing through a cow) as the state
standard. The research clearly supports this as a safe exposure limit.
The voltage and current exposure produced by ground currents are typically
100 to 1000 times lower than this level.
Wisconsin has had the most aggressive program of any state in the nation
to deal with the stray voltage concerns of the public. Stray voltage
is not a mystery. We know how to measure it and we know how to reduce
it. If you have a concern about electrical exposures on your farm, request
a measurement of cow exposure levels from your utility company. Make
sure your farm wiring and the utility wiring meets electrical safety
codes and cow contact exposure guidelines. Always remember to keep yourself
and your animals safe. Never compromise the safety of your farms electrical
system in an attempt to reduce electrical exposure levels.
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