Neutral-To-Earth Voltage

Neutral-to-earth voltage is present in nearly all farm electrical systems. It is an inherent part of the system and can never be entirely eliminated.

Dairy cows — because dairy farms use sophisticated machinery that demands large amounts of electricity — are most affected. N-E voltage has also been known to affect swine farrowing units as well as poultry and beef operations.

Voltages ranging from one volt and above can cause potential problems. Even those between one-half and one volt may affect some animals.

Dairy cows exposed to neutral-to-earth voltage can exhibit three general types of symptoms:

Behavior changes

• Hesitate or refuse to approach certain waterers, feeders, or metallic equipment.
• Hesitate to enter parlor or jump across transition joints.
• Tread, kick, or appear nervous while milking.
• Increased defecation and/or urination in milking parlor.
• Reluctant to consume water or feed.

Milking problems

• Poor milk letdown and incomplete or uneven milkout (leaving abnormal amounts of residual milk in one or more quarters).
• Increased milking time.

Poor production

• Increased mastitis.
• Lowered milk production.

It is important to remember, however, that these conditions may be caused by sources other than N-E voltage. These include poor milking practices, improperly sized or malfunctioning equipment, improper feed, poor herd health or poor herd management. All possible causes should be examined to determine the appropriate corrective procedure.

Neutral-to-earth voltage can be caused by a number of factors, both in and around the farm. The amounts of minerals and moisture in the soil, subsoil and rock strata, and the varying water table level can affect any grounding system and change N-E voltages. Sudden problems are usually due to electrical loads, conductors and connections.

Some of the factors that may cause N-E voltage include:

• A loose or corroded ground rod connection.
• Badly rusted electrical boxes or conduit (a tube or duct for enclosing electric wires or cable).
• Wires, electrical boxes, or motors in wet or damp areas.
• Accumulation of dust on or around electrical equipment.
• Bent or broken conduit.
• Scraped insulation, exposing wires.
• Insulated wires wrapped around metal pipes.
• Electrical boxes missing covers, or covers that are loose.
• Loose, hanging wires.
• Electrical outlet missing third hole for ground.
• Unbalanced electric load.
• Pinched pulsator wiring.

There are several things you can do to try to reduce neutral-to-earth voltage. Keep in mind, though, that some N-E voltage will always exist in electrical systems.

If the problem originates on the farm:

• Upgrade electrical system.
• Replace faulty equipment that may produce leakage currents.
• Install heavier equipment grounds or adequate power circuits.

If the problem originates off-farm:

• Always consult with your power supplier to work out a safe and effective solution.
• Installation of an isolation transformer on the farm may be advised – you will then assume responsibility for maintaining a proper neutral ground on the farm.

If the problem originates on and/or off-farm:

• Provide an “equipotential plane” in milking parlors as a way of eliminating the possibility of current flowing through a cow’s body.

Remember that a number of stress factors can result in decreased milk production. Therefore it is important to isolate and correct ALL causes. To accomplish this, a team approach is recommended.

1. Keep a notebook detailing problems that occur. Include the time of day, equipment in use, duration and a description of the cow’s reaction.
2. Have appropriate professionals thoroughly check your herd’s health, milking, feeding and other dairy management programs. Contact your local Cooperative Extension Office for assistance.
3. Thoroughly test the milking system and its components to ensure that they are operating correctly.
4. Have an electrician completely check the farm’s electrical system for N-E voltage. If excessive neutral-to-earth voltage is detected, repair or modify the electrical system to reduce it to a tolerable level.
5. If an off-farm N-E voltage source is the significant cause, contact your power supplier.

For more information on neutral-to-earth voltage, contact your county Cooperative Extension Office. Videotapes related to N-E voltage are also available by writing to:

The National Food and Energy Council
409 Vandiver West, Bldg. 4, Suite 202
Columbia, MO 65202

Or by calling: (314) 875-7155.