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Farm Stray Voltage

Do you own or operate a farm with livestock? If so you should be aware of the potential impacts of 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 stray voltage or animal contact voltage (ACV). Stray voltage can be produced by a wide variety of off- farm and on-farm sources.

Stray Voltage can be caused by a variety of sources including farm wiring and grounding issues, unbalanced farm load, equipment faults, or voltage from other sources such as telephone lines, gas lines and utility electrical distribution systems.

Off-the-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, HHHI’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 lightning strikes, it may result 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, improper grounding, unbalanced farm system loading, high resistive grounds, electric fences, electrical load switching, defective equipment or voltages from telephone lines or gas pipelines are all possible sources.

The effects of stray voltage animals can vary. Using dairy cows as an example, reported symptoms 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 same symptoms can also be the result of other non-electrical farm factors. For example, disease, poor nutrition, unsanitary conditions, or milking machine problems can produce some of the same symptoms in farm animals as stray voltage. Farmers should consider and investigate all possibilities, including stray voltage, when attempting to resolve these symptoms.

More information on the effects of Stray Voltage can be found on the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) website.

If the source of Stray Voltage is on your farm, you can perform mitigation measures such as installing a neutral isolating device, adding electrical bonding between contact points, upgrading wiring, or replacing faulty equipment. This work should be performed by a qualified electrical contractor and must meet the requirements of the Electrical Safety Code. If Halton Hills Hydro’s distribution system is the source of the Stray Voltage, we will take the appropriate corrective actions.

If a stray voltage problem is suspected, contact the HHHI Engineering Department at 519-853-3700 extension 213 to set up an appointment for stray voltage measurement testing by HHHI staff at the location.

Submit our online Farm Stray Voltage Investigation Request form.

For additional information about Farm Stray Voltage and basic on the farm trouble shooting please see ESA’s guide A Farmer’s Guide to Basic Troubleshooting of On Farm Stray Voltage