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Farm Customers — Stray Voltage

What is Stray Voltage?

Varying amounts of low-level voltage often exist between the earth and electrically grounded farm equipment such as metal stabling, feeders, milk pipelines or even wet concrete floors. Usually, these voltage levels present no harm to animals. However, if an animal touches two pieces of equipment that are at different voltage levels, a small electric current passes through the animal. This is known as "animal contact voltage," "stray voltage" or "tingle voltage."

Reported symptoms for dairy cows include:

• Reluctance to enter milking parlour
• Reduced water or feed intake
• Nervous or aggressive behaviour
• Uneven and incomplete milkout
• Increased mastitis
• Lowered milk production
  
• Reduced growth

These symptoms can also be the result of other non-electrical farm factors such as disease, poor nutrition, unsanitary conditions or milking equipment problems. Farmers should consider and investigate all possibilities, including stray voltage, when attempting to resolve these symptoms.

What causes Stray Voltage?

Stray voltage can be produced by a wide variety of off-farm and on-farm sources.

Off-farm sources:
In a properly functioning electrical distribution system, some voltage will always exist between the neutral system (ground conductors) and the earth. The level of this NEV (neutral-to-earth voltage) can change on a daily or seasonal basis, depending on changes in electrical loading, environmental conditions and other factors. For safety reasons, Hydro One's neutral system is connected to a farm's grounding system. While this bond protects people and animals from shocks caused by faulty electrical equipment and lighting strikes, it also results in a stray voltage equal to a fraction of the NEV appearing on grounded farm equipment, such as feeders, waterers, metal stabling, metal grates, milk pipelines and wet concrete floors.

On-the-farm sources:
Poor or faulty farm wiring, unbalanced farm system loading, improper grounding, defective equipment or voltages from telephone lines or gas pipelines are all possible sources.

If you think you have a Stray Voltage problem

Call 1 (888) 664-9376 to set up an appointment for a visit from Hydro One staff who will perform appropriate measurements to help determine if stray voltage is present on your farm. Office hours are Monday to Friday 7:30 a.m. to 8 p.m.

For more information

For additional information on the effects of stray voltage on livestock see the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) website.

Stray Voltage Solutions Guide for Electrical Contractors (PDF 275 KB)

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