Based upon results from over seven years of scientific research, The Public Service Commission of Wisconsin (PSC) adopted a new "level of concern" for stray voltage. The new "level of concern" is 2.0 milliampere (mA) for both off-farm and on-farm sources, combined. The previous level of 1.0 mA was established by the PSC in 1989. The level of concern is the amount of current above which cows start to perceive the current. Although the research indicated that the appropriate level of concern could be placed at 6.0 mA, the Commission decided it was prudent to set a more conservative, preventive level at which only a small percentage of cows would perceive any current and at which a cow's behavior, health, or milk production would not be harmed. Research results published by the United States Department of Agriculture (USDA) in 1991 indicate that only 1 percent to 5 percent of all cows can perceive any current at all at the PSC's previous level of concern, much less be harmed by it. Since the USDA results were published, studies conducted by the University of Wisconsin, Cornell University in New York, and the New Liskard College in Ontario, Canada have verified the USDA's original conclusions. The research duplicated actual field conditions, and to eliminate even the appearance of bias, no electric industry funding was accepted to conduct the research.
The scientific consensus upon which the PSC based the decision indicated that depending on its sensitivity, a cow will begin to perceive electric current at levels between 1.0 to 3.0 mA. Research indicates that current at these levels has no effect on milk production. A moderate behavioral response was found to occur at current levels between 3.0 and 6.0 mA, again depending on a cow's sensitivity to electricity. The vast majority of cows will not perceive currents at this level and will show no harmful effects.
The 2.0 mA level of concern includes all the stray voltage present in the cow contact area, not just the utility's contribution. This provides for a more equitable distribution that splits the responsibility 50-50 between the utility and the farmer. At the 2.0 mA level of concern, a utility contributing half or more of the standard (i.e., 1.0 mA or more) must reduce its portion of stray voltage so that current is below 1.0 mA.
Isolation Upon Request
The Wisconsin Commission also decided that isolating equipment should
be made available to the farmer on request for a trial period of one
year. This ensures that an entire lactating period and all seasons of
the year are included. A customer may also request permanent
isolation at anytime. The costs associated with the request are to be
borne by the customer. However, for safety reasons, prior to having
an isolator installed, the farm should be inspected to ensure it is
up to code.
The Commission determined that the utility should own and maintain the isolator and should be able to determine what type of device is installed. However, spark gap isolation devices cannot be used. An isolator will only be allowed on an operating livestock farm to address stray voltage concerns, and farmers will be required to sign a "hold harmless" clause before receiving an isolator. The farmer should pay for the installation of the isolator, but the utility should refund the salvage cost of the device if the farmer chooses not to keep the isolator after the one-year trial period. Anyone with further questions regarding this matter should contact Dan Dasho at (608) 267-6718.
This page is part of the Biosystems and Agricultural Engineering Department web at http://www.bae.umn.edu/