Idaho Administrative Code › Title IDAPA 31 - Public Utilities Commission › Rule 31.61.01 - RULES FOR THE MEASUREMENT OF STRAY CURRENT OR VOLTAGE (STRAY VOLTAGE RULES) › TESTING AND MEASUREMENT PROCEDURES › Section 31.61.01.073 - TEST 1 - COW CONTACT TEST

Current through August 31, 2023
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)