Proposed Definitions for Stray Voltage Working Group
The following definitions were taken from NEETRAC’s Stray Voltage Handbook.
Neutral-Earth Voltage (N-E Voltage, VNE)
This is the voltage measured between any point on a neutral or its extension (a connected
metallic pipe for example) and an isolated reference electrode placed in the earth with
“zero” or “nearly zero” potential, a remote earth. The neutral-earth voltage may be
different at different points on the neutral system. This is due to the flow of currents and
the resulting voltage gradients throughout the complex neutral/grounding system.
Ground Electrode Current (Ground Current, Ig)
In a multigrounded system, a portion of neutral current flows into ground (earth) via
grounding electrode system. A ground electrode system may consist of single ground rod
or interconnected multiple ground rods. An equipotential plane connected with the
service panel ground is another example of a ground electrode system.
The “ground electrode current” is the total current flowing in the surrounding earth via
the ground electrode system. Note that this is the current, which develops voltage
gradients on the surface of the earth.
Ground Electrode Resistance (Rg)
“Ground Electrode Resistance” is a resistance of a ground electrode system with respect
to remote ground (earth). By virtue of Ohm’s law, the following relationship exists:
V NE  I g xRg
Neutral Current (In)
This is the current, which flows in a neutral conductor.
Stray Voltage (Source Voltage, Open Circuit Contact Voltage, Voc)
“Stray voltage” or “contact voltage” is a small open circuit voltage (usually less than 10
volts) measured between two points that can be simultaneously contacted by a human or
an animal1. For a cow, the open circuit contact voltage can be between the mouth and
four hooves. For an adult standing and touching an outdoor faucet, this voltage can
appear between the hand and the feet.
Depending on how far the ground electrode system is from the subject making the
contact, this voltage can be as low as a small fraction and as high as the full value of the
N-E voltage responsible for the stray voltage. As an example, this voltage measured over
an equipotential plane can be 2-4 percent of the barn N-E voltage. With the equipotential
plane and the re-bars from the concrete removed, this voltage can approach the N-E
voltage value.
Closed Circuit Contact Voltage (Vcc)
“Stray voltage” or “contact voltage” when measured with the current flowing through the
human or the animal is defined as the “closed circuit contact voltage”. In dairy farm
cases, this voltage is measured across a 500  resistor and is always less than or, in the
extreme case involving a high impedance source, is equal to the open circuit contact
voltage.
Stray Current (Body Current, Contact Current, Ic)
The “stray current” or “contact current” is defined as the current passing through a human
or an animal upon contact. Note that it is not the contact voltage but the current, which is
perceived by a human or an animal.
Reference
1 USDA Agriculture Handbook 696, Effects of Electrical Voltage/Current on Farm
Animals (How To Detect and Remedy Problems), pp. 2-1, December 1991.
Note: The exact wording from the USDA Agriculture Handbook 696 is as follows:
“Stray voltage is a small voltage (less than 10V) that can be measured between two
possible contact points. If these two points are contacted by an animal or person, a
current will flow. The amount of current depends on the voltage and the circuit
impedance, which includes the source, contact, and body impedances.”