Stray Voltage Sources

The most common source of stray voltage is an elevated neutral-to-earth voltage (NEV) at the service panel. Neutral-to-earth is an elevated voltage on the neutral bus when that voltage is measured relative to an electrode placed in the earth. Neutral-to-earth voltages are a direct and unavoidable consequence of the mechanisms used to distribute electrical power. Even when wiring is up to code, neutral-to-earth voltages may be sufficiently high to cause stray voltages. Many times, elevated neutral-to-earth voltages are caused by such things as:

  • Faulty electrical equipment,
  • Improper or faulty wiring, and
  • Induced or coupled voltages.

Often, these sources result in increased neutral-to-earth voltages; and the elevated neutral-to-earth voltages, in turn, lead to stray voltages. Determining the actual source (or sources) of an elevated neutral-to-earth voltage requires specific knowledge of local on-farm and off-farm electrical systems as well as a thorough understanding of electrical power distribution systems, in general.

Damaged equipment and damaged or faulty wiring create the potential for a problem known as ground faults. Ground faults are those conditions where electric current flows to the earth and thereby creates a neutral-to-earth voltage. Ground faults caused by wiring that is partially shorted to ground could also result from connections that are damaged or wet.

Properly grounded equipment has a green insulated or bare wire that safely conducts the fault current back to the electric panel. If however, the ground wire is broken or not installed, or the connections are corroded, there is little or no path for the fault current which causes neutral-to-earth voltage.

The power lines supplying power to the farm can also be a source of stray voltage. This can occur because the utility's neutral line is connected to the neutral wire of the farm electrical system at the supply transformer.

NEV can be present on the power distribution system through:

  • Electrical load imbalance,
  • Faulty distribution lines, or
  • Static discharge on the line (this is usually weather related).

Any of these events can cause NEV on the farm and lead to a stray voltage problem.