Investigation Procedures

Knowledge of the history and circumstances surrounding stray voltage / current problems is critical to solving these problems. Before any measurements are made, these questions must be answered:

  • Who is involved? Get names, addresses, titles, telephone numbers of persons present along with the location and date of the stray voltage investigation.
  • Who has been involved? Names, addresses, professions, and telephone numbers of other individuals who may have been involved in a previous investigation. What did they have to say?.
  • When did the farmer first suspect there was a voltage problem and why?
  • Do all animals react? Or just some of them?
  • What are the reactions? Where are the reactions observed?
  • Is reaction continuous or periodic?
  • At what times of the day are problems most noticeable?
  • Are problems more noticeable in wet or dry conditions? Is it seasonal?
  • What changes have been made in farm electrical systems, operators, or animal handling procedures?
  • Do equipment operators receive shocks or see or hear sparks?
  • Has anyone taken voltage and current measurements? Where? When? By whom? What were they?
  • What recommendations were made and actions taken as result of previous investigations?
  • What's the layout? Sketch the farm layout showing locations of distribution lines, transformers, services to buildings, and grounding electrodes. Note service voltages, whether they're single- or three-phase, delta or wye, and list the size of equipment.
  • Have neighbors had electrical problems of any kind? If they have, what are the details?
  • Has lightning struck in the vicinity of the farm? Where? When?
  • What is the overall condition of the wiring and electrical equipment on the farm? Look for unsuitable equipment, signs of poor maintenance, leakage paths, corrosion, and the type and extent of neutral and equipment grounding conductors. Also take a close look at how the main and building service-entrance equipment is grounded.
  • Who has made wiring installations on the farm? (Electrical contractors, equipment installers, the farmer, anyone else?).
  • What information or assistance have the utility, electricians, or equipment suppliers provided?

Conduct a visual survey of the farmstead. Determine:

  • The layout of the electrical system,
  • How it meets electrical codes,
  • If any equipment is obviously unsafe, or
  • Any wiring problems and / or maintenance needs.

Visual inspection alone cannot confirm that existing electrical problems or safety hazards are indeed creating or contributing to stray voltage/current problems. 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.

Sources for elevated neutral-to-earth voltages include:

  • Faulty electrical equipment,
  • Improper or faulty wiring,
  • Induced or coupled voltages, and
  • Static (or capacitive) discharges.

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 come from wiring connections that are loose, damaged, wet or from damaged farm equipment.

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.