Stray Voltage |
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What we think or hear about stray voltage usually involves a cow being
exposed to small voltages between conductive objects it contacts (e.g.
water bowl, stanchion pipe, etc.) and the ground or floor where it is
standing. The voltage that exists at these locations, or between these
two surfaces, is the result of voltage gradients in the earth and on its
surface. These earth voltage gradients are an unavoidable consequence of
operating farm and utility electrical systems that are grounded for
people's safety. |
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The term stray voltage, as used in dairy farming, refers to traces
of the electric power signal that seem to have
gone astray, or off track. The signals are not lost;
to the contrary, they are very much a part of the physics of electric power
systems when these systems are connected to the earth (grounded)
for people's safety.
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Some current, however small, will flow through the earth when
electric circuits are connected to it. This current creates
voltage gradients in the earth and on its surface. A cow that touches
the earth between two points is exposed to the difference in voltage,
the voltage gradient, between those two points.
The cow may or may not feel this
voltage, depending on the magnitude and duration of the voltage exposure. |
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The phenomenon is more complicated than the
term stray voltage suggests.
This section provides a detailed and technical explanation of stray voltage in
terms of earth voltage gradients. It begins with a graphical presentation of voltage
gradients in the earth, and then outlines the sources of voltage gradients in typical
power systems. It shows how cows experience these gradients as stray voltage and how
stray voltage can be classified as either step or touch potential. The section closes
with a review of stray voltage definitions. |
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Suggestions for Reading |
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We suggest that newcomers to the issue or to this site read the pages in the order
marked to receive the clearest and most valuable presentation possible. Although an
extensive reading, it is also a fascinating scientific exploration. There are no
shortcuts to understanding the issue of stray voltage. Rather than read all of the
material presented here in one sitting, bookmark this site if necessary, and return
later to continue reading. Readers familiar with this site or with the issue should
feel free to browse areas of interest and use this material as a reference. |
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The following is the outline of the Stray Voltage section, in the sequence suggested for new readers. |
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Stray Voltage Section Outline |
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