How to minimize stray voltage problems

After it was built in 1997, production at Excel Dairy was pretty good. But, by the fall of 2001, it had dropped dramatically - down to 58 pounds of milk per cow per day, on average, compared to the 74 to 76 pounds per cow just a few years earlier.

"We were at wit's end," says Larry Amundson, owner of the 1,000-cow facility in Thief River Falls, Minn. No one could figure out what was happening. Experts looked at nutrition, management - even the water supply. Eventually, the problem was traced to stray voltage. In several locations, ground wires were carrying neutral current in an improper manner, Amundson said.

Once the wiring problem was fixed, the dairy saw its production shoot up again. "We made a huge improvement," Amundson says. Today, the cows are milking at 74 pounds-plus, on average.

Stray voltage may be robbing you of production. Rather than blaming your utility company or engaging in expensive litigation, follow these three steps to minimize problems on your dairy.

1. Proper wiring

As Excel Dairy learned, wiring can be a problem - even in a new facility.

First of all, have a qualified electrician check your farm's wiring.

Some utilities offer special incentives to update farm wiring. For instance, Wisconsin Public Service Corp. provides cost-share money and low-interest loans through its Farm Rewiring Program.

"We've been doing that for three years, and have had 800 farms that have participated in the program. It's gone really well," says Rob Ash, agriculture department manager at Wisconsin Public Service Corp., which serves northeast Wisconsin.

If extensive repairs are made, hire a state-certified electrical inspector to check the work. To find an inspector in your area, call your utility company or state department of commerce. The commerce department may include a list of inspectors on its Web site.

2. Install a neutral isolator

Stray voltage can arise from on-farm sources or off-farm sources, points out John Bass, consulting engineer and stray voltage expert from Minnetonka, Minn.

To reduce the chance of it coming from off-farm sources, ask your utility company to install a neutral isolator. (See illustration on page 24.) Basically, this device acts as a voltage-triggered switch between the farm's neutral wire and the utility company's neutral wire, blocking current flow between the two grounded systems.

And, the isolators also act as a safety device in the event of a lightning strike or electrical fault. Normally, the isolators are in an "open" mode - not allowing current through. But, when a lightning strike or some other abnormal event occurs, the device switches to a "closed" mode for a fraction of a second. This minimizes the difference in voltage between the utility's neutral wire and farm's neutral wire - an important safety factor - and sends current back to the electrical transformer or substation, helping to ensure that a fuse or a circuit breaker will clear the fault.

Isolators vary in cost, depending on the manufacturer. Cost ranges from $30, all the way up to $900. Like anything else, you get what you pay for. The more expensive models offer solid-state technology, with the ability to handle a wide range of electrical faults. Some of the less expensive models are intended simply for lightning strikes.

Check with your utility company. In some states, the utilities will put these devices in, especially if it is shown that the utilities themselves contribute to a stray voltage problem on farm.

Wisconsin Public Service Corp. will install isolators if customers request it, says spokeman Rob Ash. The customer pays a $950 one-time installation fee, then $35 per month to lease the device. That way, the customer does not have to worry about inspecting and maintaining the device - it's the utility's job instead.

3. Convert to a four-wire system

While an isolator helps prevent off-farm sources of stray voltage, a properly-installed four-wire system will help keep on-farm sources in check. (See illustration on page 26.) With a four-wire system, you are reducing stray voltage sources from the farm's electrical equipment.

With a four-wire system, you want to keep the neutral wire and grounding wire separate - except for the one connection required by the electrical code for proper grounding and safety, points out Doug Reinemann, agricultural engineer at the University of Wisconsin.

By separating the ground and neutral wires in this way, you keep the electrical current from 120-volt equipment on the
neutral wire and off of the grounding wires. This reduces the voltage on the grounding system that is connected to the metal objects in barns and parlors that cows could come into contact with.

It's a good idea to have a dedicated meter pole - located between the outdoor electrical transformer and the barn's service entrance panel - where the connection can be made between the neutral wire and the grounding wire. Locating the ground-neutral connection point away from barns and parlors helps reduce voltage levels in the cows' environment.

Unfortunately, most farms don't do these things. Usually, there is more than one connection between the neutral wire and grounding wire as the wires travel from barn to barn, which can present problems.

While a barn can have a properly designed three-wire system, the four-wire setup remains a better choice.

Remember, implementing all three steps can help reduce problems with stray voltage. When making changes, be sure to work with a qualified electrician who understands these problems and how to avoid them.  



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