Iowa Admin. Code r. 199-20.7 - [Effective 7/16/2025] Standards of quality of service
(1) Standard
frequency. The standard frequency for alternating current distribution systems
shall be 60 cycles per second. The frequency shall be maintained within limits
that will permit the satisfactory operation of customer's clocks connected to
the system.
(2) Voltage limits
retail. Each utility supplying electric service to ultimate customers shall
provide service voltages in conformance with the standard at paragraph
20.5(2)"d."
(3)
Voltage balance. Where three-phase service is provided, the utility shall
exercise reasonable care to ensure that the phase voltages are in balance. In
no case shall the ratio of maximum voltage deviation from average to average
voltage exceed .02.
(4) Voltage
limits, service for resale. The nominal voltage shall be as mutually agreed
upon by the parties concerned. The allowable variation shall not exceed 7.5
percent above or below the agreed-upon nominal voltage without the express
approval of the commission.
(5)
Exceptions to voltage requirements. Voltage outside the limits specified will
not be considered a violation when the variations:
a. Arise from the action of the
elements.
b. Are infrequent
fluctuations not exceeding five minutes in duration.
c. Arise from service
interruptions.
d. Arise from
temporary separation of parts of the system from the main system.
e. Are from causes beyond the control of the
utility.
f. Do not exceed 10
percent above or below the standard nominal voltage, and service is at a
distribution line or transmission line voltage with the retail customer
providing voltage regulators.
(6) Voltage surveys and records. Voltage
measurements shall be made at the customer's entrance terminals. For
single-phase service the measurement shall be made between the grounded
conductor and the ungrounded conductors. For three-phase service the
measurement shall be made between the phase wires.
(7) Each utility shall make a sufficient
number of voltage measurements in order to determine if voltages comply with
subrules 20.7(2), 20.7(3), and 20.7(4). All records obtained under this subrule
shall be retained by the utility for at least two years and shall be available
for inspection by the commission's representatives. Notations on each chart
shall indicate the following:
a. The location
where the voltage was taken.
b. The
time and date of the test.
c. The
results of the comparison with a working standard indicating
voltmeter.
(8) Equipment
for voltage measurements.
a.
Secondary standard indicating voltmeter. Each utility shall have
available at least one indicating voltmeter maintained with error no greater
than 0.25 percent of full scale.
b.
Working standard indicating voltmeters. Each utility shall
have at least two indicating voltmeters maintained so as to have as-left errors
of no greater than 1 percent of full scale.
c.
Recording voltmeters.
Each utility must have readily available at least two portable recording
voltmeters with a rated accuracy of 1 percent of full scale.
d.
Voltage monitors integral to
watt-hour meters. If the utility employs automated metering
infrastructure with integrated voltage monitoring, this may be used in lieu of
the equipment listed in paragraphs 20.7(8)"a,""b," or
"c" as long as the automated metering infrastructure with
integrated voltage monitoring meets the accuracy standard required for the
equipment being replaced.
(9) Extreme care must be exercised in the
handling of standards and instruments to ensure that their accuracy is not
disturbed. Each standard shall be accompanied at all times by a certificate or
calibration card, duly signed and dated, on which are recorded the corrections
required to compensate for errors found at the customary test points at the
time of the last previous test.
(10) Planned interruptions shall be made at a
time that will not cause unreasonable inconvenience to customers, and
interruptions planned for longer than one hour shall be preceded by adequate
notice to those who will be affected.
(11) Power quality monitoring. Each utility
shall investigate power quality complaints from its customers and determine if
the cause of the problem is on the utility's systems. In addressing these
problems, each utility shall implement to the extent reasonably practical the
practices outlined in the standard given at paragraph
20.5(2)"f."
(12)
Harmonics. A harmonic is a sinusoidal component of the 60 cycles per second
fundamental wave having a frequency that is an integral multiple of the
fundamental frequency. When excessive harmonics problems arise, each electric
utility shall investigate and take actions to rectify the problem. In
addressing harmonics problems, the utility and the customer shall implement to
the extent practicable and in conformance with prudent operation the practices
outlined in the standard at paragraph 20.5(2)"g."
This rule is intended to implement Iowa Code sections 476.2 and 476.8.
Notes
State regulations are updated quarterly; we currently have two versions available. Below is a comparison between our most recent version and the prior quarterly release. More comparison features will be added as we have more versions to compare.
(1) Standard frequency. The standard frequency for alternating current distribution systems shall be 60 cycles per second. The frequency shall be maintained within limits which will permit the satisfactory operation of customer's clocks connected to the system.
(2) Voltage limits retail. Each utility supplying electric service to ultimate customers shall provide service voltages in conformance with the standard at 20.5(2)"d. "
(3) Voltage balance. Where three-phase service is provided the utility shall exercise reasonable care to assure that the phase voltages are in balance. In no case shall the ratio of maximum voltage deviation from average to average voltage exceed .02.
(4) Voltage limits, service for resale. The nominal voltage shall be as mutually agreed upon by the parties concerned. The allowable variation shall not exceed 7.5 percent above or below the agreed-upon nominal voltage without the express approval of the board.
(5) Exceptions to voltage requirements. Voltage outside the limits specified will not be considered a violation when the variations:
a. Arise from the action of the elements.
b. Are infrequent fluctuations not exceeding five minutes, duration.
c. Arise from service interruptions.
d. Arise from temporary separation of parts of the system from the main system.
e. Are from causes beyond the control of the utility.
f. Do not exceed 10 percent above or below the standard nominal voltage, and service is at a distribution line or transmission line voltage with the retail customer providing voltage regulators.
(6) Voltage surveys and records. Voltage measurements shall be made at the customer's entrance terminals. For single-phase service the measurement shall be made between the grounded conductor and the ungrounded conductors. For three-phase service the measurement shall be made between the phase wires.
(7) Each utility shall make a sufficient number of voltage measurements in order to determine if voltages are in compliance with the requirements as stated in 20.7(2), 20.7(3), and 20.7(4). All records obtained under this subrule shall be retained by the utility for at least two years and shall be available for inspection by the board's representatives. Notations on each chart shall indicate the following:
a. The location where the voltage was taken.
b. The time and date of the test.
c. The results of the comparison with a working standard indicating voltmeter.
(8) Equipment for voltage measurements.
a. Secondary standard indicating voltmeter. Each utility shall have available at least one indicating voltmeter maintained with error no greater than 0.25 percent of full scale.
b. Working standard indicating voltmeters. Each utility shall have at least two indicating voltmeters maintained so as to have as-left errors of no greater than 1 percent of full scale.
c. Recording voltmeters. Each utility must have readily available at least two portable recording voltmeters with a rated accuracy of 1 percent of full scale.
(9) Rescinded IAB 12/11/91, effective 1/15/92.
(10) Extreme care must be exercised in the handling of standards and instruments to assure that their accuracy is not disturbed. Each standard shall be accompanied at all times by a certificate or calibration card, duly signed and dated, on which are recorded the corrections required to compensate for errors found at the customary test points at the time of the last previous test.
(11) Planned interruptions shall be made at a time that will not cause unreasonable inconvenience to customers, and interruptions planned for longer than one hour shall be preceded by adequate notice to those who will be affected.
(12) Power quality monitoring. Each utility shall investigate power quality complaints from its customers and determine if the cause of the problem is on the utility's systems. In addressing these problems, each utility shall implement to the extent reasonably practical the practices outlined in the standard given at 20.5(2)"f. "
(13) Harmonics. A harmonic is a sinusoidal component of the 60 cycles per second fundamental wave having a frequency that is an integral multiple of the fundamental frequency. When excessive harmonics problems arise, each electric utility shall investigate and take actions to rectify the problem. In addressing harmonics problems, the utility and the customer shall implement to the extent practicable and in conformance with prudent operation the practices outlined in the standard at 20.5(2)"g. "
This rule is intended to implement Iowa Code sections 476.2 and 476.8.