Measuring stray voltage on the farm

Stray voltage, a common phenomenon, most likely will be found if you look for it. In other words, all farms with electrical service have some level of stray voltage. WPS can help you determine if the levels on your farm are affecting your livestock.

A stray voltage test using protocol developed by the Public Service Commission of Wisconsin is the only way to give you the answers that you need. WPS knows where and what to measure, knows what types of sources to look for, and has the equipment and expertise to conduct the most comprehensive stray voltage test available to you.

How WPS measures stray voltage

WPS tests for stray voltage for a period of 24 to 48 hours to measure all levels of electric load during a typical day.

Voltmeters are positioned where livestock touch two contact points simultaneously. By doing this, WPS measures the actual voltage levels that livestock encounter, in addition to voltage at other points on the electrical system.

  • The handheld Fluke 87 meter allows us to locate cow contact points with the highest voltage. WPS then uses these spots - certain stalls, for example - to conduct the tests. By testing in areas with the highest readings, we know that the "worst-case scenario" is being recorded.
  • WPS places its main digital voltmeter (Metrosonics MSRV4) near an area where readings can be observed. This meter reads both steady-state and impulse (motor start) voltages. The Metrosonics records measurements on four channels:
    1. Primary neutral to a remote ground rod
    2. Main service panel neutral to a remote ground rod
    3. Voltage drop in the neutral wire between the primary transformer and the main service panel. (The higher the voltage drop, the stronger the chance for stray voltage problems.)
    4. Cow contact voltage
  • A handheld, clamp-on ampmeter is used to measure currents on neutral conductors.
  • A handheld oscilloscope displays instant readings of voltage impulses that may be caused by fencers, trainers or motors.

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Cow contact measurements

WPS takes measurements where livestock may encounter stray voltage as they simultaneously touch two points, such as:

  • Water bowl to floor
  • Water bowl to stall
  • Stall or parlor steel to floor
  • Heated waterer to floor
  • Feed bunk to floor

When the floor is a contact point, a wire from the meter is connected to a copper plate pressed down onto a clean spot on the concrete floor. Salt and water may be used to increase conductivity of the floor.

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Determining the source

WPS diagnoses the source of stray voltage by measuring the voltage at the primary and secondary neutral, and also by measuring the voltage drop between these two points. A remote ground rod is used as a reference. The reference rod is driven into the ground at least 100 feet from a primary or secondary panel or an electrical ground. By taking these readings, we can determine the source of any excessive voltage and work with you on corrective actions that may need to be taken.

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Testing timeframe

By testing for 24 to 48 hours straight, WPS is sure to record the highest levels of stray voltage, such as when the milk pump motor is started during milking. The Public Service Commission of Wisconsin requires electric utilities to test for a minimum period of 24 hours.

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Schedule a free stray voltage test

Our comprehensive stray voltage test is free. Schedule an appointment to have your WPS agricultural consultant and a WPS electrical engineer visit your farm and conduct the test. Once testing is complete, WPS will provide you with a printout of the actual voltmeter readings and discuss the findings with you. If the utility is found to be the source of any excessive stray voltage, WPS will fix the problem. If the on-farm electrical system is found to be the cause, we will work with you to reduce the level of stray voltage.

To make an appointment, contact us.

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