Section 460.2707. Protocol to evaluate utility contribution to animal contact current

(1) The following shall be the  protocol  for  testing  animal contact current when the utility utilizes a grounded distribution system with a primary neutral conductor, except that a utility may submit an alternative protocol to the commission for approval to determine the utility contribution to animal contact current:

(a)      Identify animal contact location to be tested.

(b)           Measure and record the steady state animal contact voltage (AcV) at the animal contact location concurrently with the neutral-to-earth voltage at utility primary distribution system (NpEV) and at the animal building panel (NbEV) for a period of 72 hours during a mutually agreed upon time frame to determine the maximum probable level of animal contact current  under  normal operating conditions.

(c)       Determine the highest level of animal contact voltage that occurred during the 72?hour monitoring, and the primary neutral-to-earth voltage at the utility transformer location that occurred at that same time.

(d)      Turn off farm electrical load and apply a temporary electrical load at the utility transformer to produce the same level of neutral-to-earth voltage at the utility transformer as found in subdivision (c) of this subrule. Measure the animal contact voltage again.

(e)        Using the animal contact voltage measured in subdivision (d) of this subrule, compare it to the animal contact voltage measured in subdivision (b) of this subrule to determine the  utility contribution  to  animal  contact current using Ohm's law.

(2)      The following measurement and monitoring procedures shall be used:

(a)          Conduct an evaluation of animal contact voltage (AcV) to determine the location that may result in the maximum probable current flow through the animal. This location shall be called the chosen animal contact location and shall be monitored for a period of 72 hours during a mutually agreed upon time frame. The following shall apply:

(i)         Identify all probable animal contact locations where an animal is likely to simultaneously make contact with 2 points between which a voltage may be present. This  includes  locations  of  concern  identified  by the complainant.

(ii)             Measure animal contact voltage (AcV) with a nominal 500-ohms shunt resistor (R shunt) placed across the input leads  of  the  voltage measuring instrument.

(iii)       Measurements to the floor or earth shall be made with a metal plate with an area of 12 to 16 square inches, and with a conductive material between the metal plate and the floor or earth.

(iv)         Measuring instruments shall be capable of digitally recording necessary measurements to determine the steady state voltage. Measuring instruments shall be calibrated to factory specifications by a recognized and certified laboratory. The commission shall determine the acceptability of each measuring device. The data recorded shall become part of the report.

(b)          Establish the locations from which to  monitor  neutral-to-earth voltage (NpEV and NbEV) measurements.   The following procedures shall be followed:

(i)        Establish an earth reference ground by installing a metal rod or pipe, with a diameter not less than ½ inch, in the earth to a  depth  of  not less than 1 foot and located

not less than 50 feet from any underground water pipes, utility lines, metal equipment making contact  with  the  earth,  or grounding electrodes of any electrical system.

(ii)         Determine which farm electrical panel serves the equipment or general location of the animal contact location. This electrical panel shall be called the animal building panel. The neutral-to-earth voltage  at  the animal building panel (NbEV) shall be measured from the panel grounding terminal to the reference ground established in subdivision (b)(i) of this subrule. This measurement can be used to validate that the animal contact voltage (AcV) was not inadvertently disconnected or  disturbed  during the 72-hour monitoring period.

(iii)              The neutral-to-earth voltage at the utility's primary distribution neutral conductor (NpEV) shall be measured from the utility's primary neutral grounding electrode conductor at the utility transformer serving the farm to the reference ground established in subdivision (b)(i) of this subrule.

(c)         Simultaneously measure and record the 3 steady state voltages, AcV, NpEV and NbEV, for a period of 72 hours during a mutually agreed upon time frame. If more than 1 instrument is used, then the instrument clocks shall be synchronized. The following shall be used:

(i)        The animal contact voltage (AcV) with  a  nominal  500-ohm  shunt resistor (R shunt) placed across the input leads of the voltage measuring instrument.

(ii)       The neutral-to-earth voltage at the animal building panel (NbEV).

(iii)        The neutral-to-earth voltage of the utility primary distribution system neutral (NpEV) at the utility transformer serving the farm.

(3)        Determine the utility contribution to animal contact current. This procedure may be conducted using non-recording digital voltage  measuring instruments.   All of the following apply:

(a)         Examine the voltage recordings and locate the highest steady state value of animal contact voltage (AcV) which will be called the animal contact test voltage (AcVt).

(b)           Determine the steady state value of utility primary distribution system neutral voltage (NpEV) that was present at the time the animal contact test voltage occurred. This will be called the primary neutral-to-earth test voltage (NpEVt).

(c)          Install 1 voltage instrument to measure the voltage of the utility primary distribution system neutral to the reference ground (NpEV) and another voltage instrument to measure the animal contact voltage (AcV) with a nominal 500-ohm shunt resistor (R shunt) placed across the input leads of the voltage measuring instrument.

(d)        Turn off all farm electrical loads while leaving the transformer energized and leaving the secondary neutral conductor connected to the farm electrical system. This can be accomplished by opening the  main  farm electrical disconnect and removing the  electric meter,  or by some other effective means.

(e)        Add a temporary load to the transformer (that does not utilize the secondary neutral) until the primary neutral to reference ground test voltage (NpEVt) is achieved, and record the animal contact voltage that occurs. This measurement will be called the utility contribution to animal contact voltage (AcVu).

(f)       If the primary neutral to reference test voltage (NpEVt) cannot be achieved as described in subrule 3(e) of this rule, then the utility contribution to the animal contact voltage (AcVu) will be determined by using the linear relationship between the primary neutral  to  reference voltage

(NpEV) and the animal contact voltage (AcV) with and  without  the   temporary load applied to the transformer where the following apply:

(i)       AcVo means the animal contact voltage measured with all  farm electrical loads turned off as determined in (d) of this subrule.

(ii)             AcVtemp means the animal contact test voltage as determined  in subdivision (e) of this subrule at the level of temporary load applied.

(iii)        NpEVo means the primary neutral-to-earth voltage with all farm electrical loads off as determined in (d) of this subrule.

(iv)              NpEVt means the primary neutral-to-earth voltage as determined in subdivision (b) of this subrule.

(v)             NpEVtemp means the primary neutral-to-earth voltage as determined in subdivision (e) at the level of temporary load applied.

(g)       If paragraphs (i) to (v) of subdivision (f) of this rule apply, then the utility contribution to animal contact voltage (AcVu) shall be scaled by multiplying the change in animal contact voltage (AcV) resulting from the temporary load at the utility's transformer (AcVtemp - AcVo) by the ratio of (NpEVt - NpEVo) divided by (NpEVtemp - NpEVo).  The  resulting  scaling   in animal contact voltage shall be added to the animal contact voltage (AcVo) to determine the utility contribution to animal contact  voltage (AcVu)  as follows:

(i) AcVu = {[(NpEVt - NpEVo) / (NpEVtemp - NpEVo)] x (AcVtemp - AcVo)} + AcVo.

(h)    Animal contact current contributed by the utility system (AcCu) is determined by using Ohm's law. To determine the current contributed by the utility, divide the utility contribution to animal contact voltage (AcVu) by the value of shunt resistance or R shunt. The formula for determining AcCu is AcCu amps = AcVu volts / R shunt ohms.

History: 2007 AACS.