Agricultural Stray Voltage Investigations

Agricultural Stray Voltage is a well documented and costly problem that can destroy dairy farmers and other livestock operators.

Holstein cows feeding in a stanchion barn - Animals are exposed to microshock when their body makes contact with a metal frame.

Stray Voltage is easy to detect, relatively inexpensive to correct and can bankrupt a dairy farm if ignored!

The affects of stray voltage on livestock is dramatic losses in milkfat production, bovine mastitis and refusal to eat or drink from feeding systems.

When caused by the utility, it is common that an Electrical Utility will connect the primary and secondary neutrals on their transformers causing stray voltage, the cost to isolate them is about $100.00.

Electrical Hazard Sign Symbol

What Causes Stray Voltage?

Stray voltage or "microshock" appears anytime that electrical current flows through the buildings grounded pipes and other metal components.

Agricultural Stray Voltage can be caused by either the electrical utility or the on farm wiring or both.

Common causes from the farm include:

The neutral conductor is grounded at more than one point in the system.
Incorrect wiring of transformers.
The use of auto-transformers.
Old style motors that use the motor frame as a conductor.
Old 240 volt appliances that connect the neutral to the appliance chassis.
High resistance shorts to ground in electrical panels and boxes.
RF filters on motors and other components.
Incorrectly wired motor starters.
Not using a four wire electrical distribution system for single phase systems or five wire for three phase electrical systems on the farm.
Defective equipment.
Interaction between motors, transformers, equipment and even other buildings on the farm.

Common cause from the Electrical Utility:

The Electrical Utility causes stray voltage when they connect the neutral on the primary side of the transformer serving the farm to the neutral on the secondary winding of the transformer. This is the standard connection specified in the National Electrical Safety Code (NESC) which governs the utilities. The National Electrical Code (NEC), which covers the on farm wiring, requires that the secondary neutral be hard wired to the buildings water system, structure and electrical ground rod. Therefore, the voltage level of the building structure and water system is elevated to the voltage level of the primary neutral conductor on the utilities electrical distribution network. This voltage can be significant and is the primary cause of Stray Voltage on a farm.

Farms and Concentrated Animal Feeding Operations(CAFO) are a special case because the stray voltage level can become so high that people and animals can actually feel the electrical shock.

Fortunately, stray voltage is also easy to measure and inexpensive to correct once you have identified the cause. Stray voltage is the name that has been given to the occurrence of voltages between some conductive surfaces in a barn or other building. Stray voltage can be caused by the Electrical Utility, Farm Wiring or by Defective Equipment. The Stray Voltage hazards are similar to Microshock hazards, except the hazard level is much higher, starting at about 1/2 Volt.

GBI has the expertise and analytical tools to pinpoint the cause and eliminate stray voltage from those farms having a problem. Every year farmers spend and loose a lot of money on quick fixes that don't work. Stray Voltage is a technically complex problem that requires good engineering to eliminate and prevent recurrence.