01.
Purpose. This test is to determine the location(s), if any, where stray
current or voltage exceeds the PAL and to identify the location(s) at which the
cow contact voltage will be recorded in the forty-eight (48) hour test.
(4-6-23)
02.
Selection of Cow
Contact Points. The selection of cow contact points to be tested shall
include a sufficient number of locations reasonably likely to demonstrate the
presence of stray voltage or current, if any. (4-6-23)
03.
Conducting the Test. The
voltage across the shunt resistor or current through the shunt resistor shall
be measured between cow contact points as shown in Figure 1. The source
resistance shall be calculated during analysis for all cow contact points.
(4-6-23)
a. When using a voltmeter to measure
voltage between contact points where one (1) of those points is the floor
surface, the equipment shall be arranged as shown in Figures 1 and 2, using a
metal plate, which shall make a high quality conductive contact with the ground
or floor. If the service provider is unsure of having a high quality conductive
contact with the floor or ground, then the procedure described in Paragraph
073.03.c. shall be followed. If necessary, corrosion shall be removed from the
point(s) where test lead(s) make contact with metal equipment.
(4-6-23)
b. When using an in-line
milliammeter or a clamp-around milliammeter to measure current between contact
points and one (1) of those points is the floor surface or earth, the equipment
shall be arranged as shown in Figure 3, using a metal plate which shall make
high quality conductive contact with the ground or floor. If the service
provider is unsure of having a high quality conductive contact with the floor
or ground, then the procedures described in Paragraph 073.03 .c. shall be
followed. If necessary, corrosion shall be removed from the point(s) where test
lead(s) make contact with metal equipment. (4-6-23)
c. A metal plate used to make an electrical
contact with the earth or floor shall be of regular shape (square, rectangular
or round), and shall have a surface area equal to or greater than sixteen (16)
square inches (4 inches x 4 inches or equivalent). Place a weight not less than
twenty (20) pounds on the metal plate. This weight shall be applied evenly
across the metal plate and not to the adjacent concrete or earth. Place the
metal plate a minimum distance of twelve (12) inches from any metal equipment
making contact with the floor or earth. (4-6-23)
i. Where the metal plate is to be placed on a
concrete floor, the surface shall be flat. Clean the floor surface with a stiff
brush to remove debris that may add excess resistance. Use water to clean the
floor surface at the point where the metal plate will be placed. Place a paper
towel or similar material soaked in saltwater between the metal plate and the
concrete floor. (4-6-23)
ii. Where
the metal plate is to be placed on the ground or earth surface, the surface
shall be flat. Remove any debris and add water to the area, if necessary, to
dampen the soil. The surface of the metal plate that will make contact with the
earth shall be clean and free of corrosion before use. Remove any corrosion, if
necessary. (4-6-23)
04.
Recording the Data. The
person conducting this test shall record the location of, and measured values
at, each test point. At each cow contact location, an open circuit voltage
reading (Voc) and a voltage with five hundred (500) ohm nominal shunt resistor
placed across the input to the meter (Vshunt) shall be taken. These readings
shall be taken with ten (10) seconds or less time between each reading.
Alternatively, a current measurement (Ishunt) may be taken in place of the
voltage reading (Vshunt) . Data for these test points shall be recorded on the
form in Appendix 1. (4-6-23)
05.
Source Resistance Calculation. The source resistance (Rsource)
shall be calculated for each cow contact location measured and the value
recorded in Appendix 1. The following formulas shall be used to calculate
source resistance.
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(4-6-23)
