Frequently Asked Questions
What is stray voltage?Stray voltage is a low level of voltage that animals may encounter in their normal activities. If an animal simultaneously contacts two surfaces with a voltage difference, a small electrical current can flow through the animal. A common example is when an animal touches both an electrically connected point (watering cup) and the concrete floor (earth).
Download the Stray Voltage Checklist
Download “Stray Voltage Detection: A Self-Help Guide”
|
 |
|
How can stray voltage affect an animal? An avoidance behavior can occur when an animal comes into contact with stray voltage at a level that it can feel. At higher voltage levels, behavior changes can be severe enough to limit milk production or growth in livestock. What causes stray voltage? Stray voltage is a naturally occurring phenomenon due to the operation of farm electrical systems and utility distribution systems. A small amount of stray voltage will be present with all properly grounded electrical systems. Any metallic structure or surface may become a pathway for electrical current carried on the neutral and grounding systems. What are common sources of stray voltage? The sources of the current or voltage may be on-farm, off-farm, or a combination of the two. In many cases, there is more than one source. Some sources may include:
|
|
How is stray voltage measured?
To estimate the current that may flow through an animal, a resistor is placed in the testing circuit where the animal would be, and voltage is measured across it.
A standardized measurement of stray voltage is defined as "the voltage measured across a 500 ohm (nominal) resistance connected between two animal contact points."
The 500-ohm resistor is used to simulate the worst case or lowest resistance of the animal circuit.
What level of stray voltage is a concern?
The Public Service Commission of Wisconsin has determined that if a voltage difference of 1.0 volt AC or more between animal contact points (measured with a 500 ohm resistor in the circuit), action should be taken to reduce this voltage.
How do I know if stray voltage is a problem on my farm?
Use our Stray Voltage Checklist to identify potential trouble spots:
Download the Stray Voltage Checklist
[PDF format - one page, 24kb]
In addition, a properly installed stray voltage meter should be standard equipment on a dairy farm. Your Alliant Energy Ag Services representative can assist you with buying a permanent meter and consult with your electrician for installation.
Other types of voltmeters can be used for "spot checks". For detailed information on metering and analyzing stray voltage, read Stray Voltage Detection: A Self-Help Guide published by the Midwest Rural Energy Council.
Download “Stray Voltage Detection: A Self-Help Guide”
[PDF format - 11 pages, 55kb]
How can I prevent stray voltage?
While stray voltage can never be completely eliminated, you can take steps to reduce the levels.
Evaluate your electrical system with the “self-help guide” listed above and have a stray voltage investigation completed by your Alliant Energy Agricultural Representative. The rep will determine the causes of the stray voltage levels on your farm.
If Alliant Energy's utility distribution system contributes 0.5 volts or more to the cow contact voltage as determined by a load test of 20 kW (approximately 27 hp) of 240 volt load, Alliant Energy will modify its electrical system until animal contact voltages are less than 0.5 volts.
If cow contact voltages are due to the wiring on your farm, your Ag Services representative will offer consultation to you and your electrician.
Learn more about on-site stray voltage consultations
Contact your Ag Services representative to learn more about stray voltage