Stray Voltage and Dairy Barns

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Electricity has helped make the dairy industry what it is today. But, the use of electricity can not be taken lightly. Runestone Electric has been working with dairy farmers to diagnose and mitigate stray voltage for nearly two decades. In the early years there was little information on the appropriate testing procedures, mitigation methods, and levels of concern. After literally hundreds of scientific studies and reports on the subject, it is safe to say that stray voltage is a well documented and well understood aspect of dairy farming.

Q. What is stray voltage?

A. Stray voltage is a low-level voltage (less than 10 volts) present on metal equipment that has been either grounded to the electrical system or connected to the grounded neutral conductor. Although stray voltage is present on all active distribution systems, humans usually do not notice it. Some types of livestock — especially dairy cows — are particularly sensitive to it.

Stray voltage is not EMF (electric and magnetic fields). EMF is a normal consequence of anything that uses electricity (such as a table lamp) or carries electricity (including power lines and a farm’s wiring). EMF does not cause or affect stray voltage in any way.

Stray voltage is defined as a small voltage (less than 10 volts) that can be measured between two possible contact points. If these two points are contacted by an animal, a current will flow through the animal. Depending upon the magnitude of the current the animal will respond accordingly.

Q. What are the symptoms?

A. A dairy cow affected by stray voltage may show symptoms such as:

nervousness during milking
reluctance to use waterers or feeders
unexplained drops in milk production
avoidance of metal objects

However, dairy producers should remember that these behavior changes also can occur due to problems with milking equipment, changes in milking routine, spoilage of feed or pollution of drinking water. Therefore, all potential sources for behavioral changes should be investigated.

Q. What causes stray voltage?

A. Causes can vary. Some common sources are found both on and off the farm.

improper wiring
poor grounding
unbalanced 120 volt loads
faulty equipment
poor or corroded connections

Because of high electric use, high humidity and corrosive silage acids, urine and manure, a dairy farm is not the ideal environment for electrical wiring and equipment.

Q. What should I do if I suspect stray voltage on my farm?

A. Start the problem-solving process by taking all of the following actions:

Contact Runestone Electric and explain your concerns. REA offers stray voltage investigation at no charge. Have a licensed electrician inspect the wiring on your farm. Remember that the safety concerns related to some wiring problems are more important than the stray voltage problem. By correcting safety hazards, you may solve a large part, if not all, of your stray voltage problems. Have your milking equipment dealer check out your milking system. Contact your veterinarian to help you address any herd health concerns.

Additional reading on stray voltage