Gradient Control - Equi-potential Planes

Equi-potential planes control gradients by eliminating the ground potential differences across areas of the farmstead. This process negates the effects of all neutral-to-earth voltages in livestock facilities if the potential differences at all possible animal contact points are reduced to an acceptable level.

The electric industry uses gradient control to minimize the risk of hazardous step (foot to foot) and touch (hand to foot) potentials under fault conditions at substations and around electrical equipment. In addition to protecting people, animals, and equipment under fault or lightning conditions, properly installed equi-potential systems in livestock facilities can solve stray voltage and current problems.

The definition of the equi-potential plane is derived from two words. Equi-potential means having the same electrical potential (or voltage) throughout. Any animal standing on a properly installed equi-potential plane will have all possible contact points at or very near the same electrical potential. A properly installed equi-potential plane must include all of the following:

  • Equipment grounding,
  • Metalwork bonding, and
  • A conductive network in the floor bonded to the electrical system grounding.

It may also require entrance and exit transition ramps.

An animal may receive a shock when it steps off or onto an equi-potential plane to or from an area beyond the perimeter. A properly constructed voltage ramp will reduce the magnitude of the current flow through the animal by providing a more gradual change in voltage at the perimeter of the plane. The voltage difference between the animal's front and rear hooves cannot be totally eliminated as it moves on or off the plane; however, the difference can normally be reduced to an acceptable level.

All concrete floors installed in new or remodeled livestock facilities should include an equi-potential plane. There are two practical ways to retrofit existing facilities with equi-potential systems. One way is to fabricate the equi-potential plane over the existing floor in the facility and cover it with 2 inches of concrete. However, rebuilding the floor and system is recommended. Alternatively, it is possible to saw grooves in an existing concrete floor and grout in copper conductors, interconnect the conductors and the metalwork in the facility, and then ground the entire system to the service entrance.