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1209 PD: CAUTION: Stray voltage

Alisa Anderson Published on 05 August 2009

Two years ago, Brent and Travis Tollerud of Pelican Rapids, Minnesota, bought an existing dairy facility to replace the older facility their father had used.

They moved their cows into the facility that fall. After they’d gone through problems associated with transitioning, their cows still weren’t producing well. The Tolleruds tried everything they knew how to do, but the cows still didn’t improve.

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“The biggest symptom was the cows weren’t drinking enough water, and that caused all the other problems. Our problems got worse in the winter. Our somatic cell count went way up, our cases of clinical mastitis increased ten-fold, and the cows wouldn’t respond to treatment. Our death loss was over 50 percent, and that isn’t typical. Things weren’t making sense in how the cows were responding,” Brent says.

The Tolleruds finally realized that their problems weren’t coming from how they were managing. It was something else that they could only see by watching the response of the cows.

“In the parlor the cows were jumpy and kicky. Just watching the cows drink water, I would see that they would bob their noses in and out of the water. They wouldn’t just put their noses in and drink. A few cows will do that, but in general they want to drink water,” Brent says.

After trying everything else they knew, the Tolleruds discovered that they had small amounts of stray voltage in their new facility. The voltage was not high enough to shock humans, but cows are more sensitive to electrical currents passing through their body. A cow will be affected at .35 volts, but a human can be affected by a current as low as three volts. Any kind of moisture will reduce resistance in cows and people by more than half. Signs of stray voltage can include refusal to enter the milking parlor, refusal to cross a crack in the concrete, a dull coat and eyes, undue nervousness and poor feed and water intake.

“Because we were having stray voltage problems we opened up the barn door to give them the choice to come in the barn or out. They would choose to stand out in the snowstorm rather than come in the barn,” Travis says.

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As more and more electricity is used, the chances of stray voltage affecting the dairy become greater, especially in older facilities where the wiring is old and may not be able to handle the current electrical usage.

“I would say the biggest thing is people are not aware of it. We were told we probably had stray voltage. I guess we kind of brushed it off because the cows were breeding back, the somatic cell count was dropping at that time and it seemed like things were starting to improve. Then the cold weather came again and everything fell apart. We were forced to deal with it,” Travis says.

The Tolleruds called the utility company to come out and check on things. But there wasn’t anyone that understood stray voltage enough to help them. Fortunately the Tolleruds were able to contact Chuck Untiedt, another dairy farmer who had experienced stray voltage at his farm and who now helps other dairy producers with their stray voltage problems. Together they are working to fix the problems and get their farm back up to its former production level.

Dealing with stray voltage can be stressful, so it is far better to avoid it in the first place, Untiedt says. When building a new facility or transitioning to one, a key to avoiding problems is to have a qualified electrician make sure the electrical wiring is at least up to code. This is especially essential in an older facility. But even that may not be enough.

“The code is there for safety, and it’s absolutely crucial to use electricity safely. But the National Electrical Code is the minimum standard. It’s not the optimum or the highest attainable. It’s not a question of if it’s going to fail – it is going to fail at some time. You want it to fail safely, so that you can get it repaired and corrected and so that it doesn’t get to the cows or the people. We tell the dairy farmers they’re going to have to exceed code,” Untiedt says.

Paul Sunde, an area supervisor of electrical inspectors in Minnesota, has a few suggestions for optimum electrical wiring. If your wiring is a single-phase system (two hot wires), he says it is best to have a four-wire system (two hot wires, a neutral and a ground wire) as opposed to a three-wire, single-phase system (two hot wires and one neutral wire). But if your wiring is a three-phase system (three hot wires), then the best setup would be with five wires (three hot wires, a neutral and a ground wire). The neutral and the ground wire should not be connected except at the distribution point (transformer). Sunde also suggests that dairy producers use copper wire instead of aluminum. Although aluminum is cheaper, it is more likely to fail. Installing an isolator at the distribution point will also provide added protection.

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“Stray voltage is in its name – it’s straying away from where it’s supposed to go. All current is supposed to be spent, meaning it goes out and it comes back, and it’s all trying to get back to where it was produced, and that is the utility generating plant where it was produced,” Sunde says.

So when electricity escapes from the wires and paths it’s supposed to take, it uses the earth as a conductor, using anything in its path to return, including dairy facilities. Large amounts of electricity sometimes escape through the grounding at distribution points. While grounding is necessary, drops in voltage or extremely high surges can cause large amounts of voltage to escape into the earth, which then seeks its way back to the substation, sometimes passing through a farm.

“Once electricity has gone into the earth, it is out of our control,” Untiedt says.

Don Johnson, an electrical engineer from Wyoming, helped Untiedt solve his stray voltage problems. He suggests that dairy farmers be careful about the location they choose to build their facilities to avoid stray voltage in the first place.

“What I would do is first determine how close the high-voltage power lines are, and if I could avoid those at all and stay out of that main path, that would help. If a farmer could actually go out before they even plan to build the barn and take some measurements and analyze it before he actually puts his investment in, that would be best. If they have to put it there anyway, then they have to work with the utility. If there are significant voltages measured, they need to work with the utility to isolate that neutral grounding, if they can at all,” Johnson says. PD

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