Current through Register Vol. 35, No. 18, September 24, 2024
A.
Request tests: Upon request by a customer the utility shall test
the meter serving that customer. The utility shall advise such customer that
they may be present during the meter test. If the meter has been tested within
the last 18 months the utility may charge the customer the applicable amount
provided for in its filed rules, such charge to be refunded to the customer
whenever the meter proves to be in excess of two percent in error.
(1) The customer or their representative may
be present when their meter is tested if such customer's request to be present
is made at the time of their request for the meter test. The utility shall give
the customer reasonable advance notification as to the day, time, and place of
the test.
(2) A report of the test
results shall be made to the customer within a reasonable time after the
completion of test, and a record of the report together with a complete record
of each test shall be kept on file at the office of the utility for as long a
period as prescribed in Subsection K of 17.9.560.14 NMAC.
B.
Pre-installation inspections and
tests:
(1) Every meter not certified by
the manufacturer shall be inspected and tested in the utility's meter shop
before being placed in service, and the accuracy of each of these meters shall
be adjusted to be within the tolerances permitted by Subsection H of
17.9.560.14 NMAC.
(2) If a meter is
physically removed from a customer's premises except for field testing and has
not been tested during the preceding thirty-month period, it must be returned
to the utility's meter shop and inspected and tested as above before it is
again placed in service.
C.
Post-installation inspections and
tests: The utility shall employ such qualified personnel and shall
conduct such post-installation inspections as may be necessary to insure an
overall accuracy within two percent of the condition as prescribed in Paragraph
(6) of Subsection H of 17.9.560.14 NMAC in the following installations:
(1) meters with associated instrument
transformers and phase shifting transformers;
(2) kilovar-hour meters, if associated with
instrument transformers;
(3) demand
meters, if associated with instrument transformers; and
(4) direct current watt-hour
meters;
(5) The commission may
order inspections when in its opinion such inspections are necessary.
D.
As-found tests:
All meters shall be tested after they are physically removed from service if
they have not been tested during the preceding thirty-month period. Excepted
are those meters damaged beyond testing. Such tests shall be made before the
meters are adjusted, repaired, and calibrated. It will not be mandatory to test
meters scheduled for retirement unless there is cause to suspect that there
will be a subsequent complaint involving the accuracy of the meter.
E.
In-service performance tests:
(1) General: In-service performance tests
must be made in accordance with Paragraph (2) of Subsection E of 17.9.560.14
NMAC. These tests may be made on the customer's premises or in the utility's
meter shop. All self-contained single-phase meters and three-wire network
meters on a utility's system must be tested in accordance with Subparagraphs
(a) through (e) of Paragraph (2) below.
(2) Periodic test schedule: In the test
intervals specified below the word "years" means calendar years and the word
"months" means calendar months. The basic periodic test interval shall not be
longer than provided for in the following schedule.
(a) Alternating current watt-hour meters:
(i) meters used with instrument transformers:
polyphase meters - at least once in four years, and single-phase meters - at
least once in eight years;
(ii)
self-contained polyphase meters - at least once in six years;
(iii) self-contained single-phase meters - at
least once in eight years.
(b) All self-contained single-phase meters
and three-wire meters must be tested in accordance with any one of the
following listed permissive test programs referred to in 8.1.8 of the standard
code for electricity metering, ANSI standard C-12-1965:
(i) periodic interval program;
(ii) variable interval program;
(iii) statistical sampling program.
(c) Variable interval and
statistical sampling programs can be used only when specifically approved by
the commission and when in accordance with the specific program adopted by
commission.
(d) Var-hour meters:
same as the schedule for associated watt-hour meters.
(e) Demand meters:
(i) block-interval non-recording demand
meters and registers - same as the schedule for associated watt-hour
meters;
(ii) block-interval graphic
watt-hour demand meters - two years;
(iii) block-interval pulse-operated recording
demand meters - two years;
(iv)
lagged-demand meters - same as the schedule for associated watt-hour
meters.
(f) Secondary
standards:
(i) portable rotating standard
watt-hour meters - 12 months;
(ii)
indicating voltmeters - 12 months;
(iii) instrument transformers - 10
years.
(g) working
standards and instruments.
(i) portable
rotating standard watt-hour meters - one month;
(ii) indicating voltmeters - six
months;
(iii) instrument
transformers - 10 years.
F.
Instrument transformer tests:
All instrument transformers shall be tested in accordance with the applicable
procedures of American standard requirements, terminology and test code for
instrument transformers, ANSI standard C-57.13:
(1) when first received except in cases where
a certificate of test is furnished by the manufacturer;
(2) when removed from service if there is
subsequently found to be visual evidence of damage;
(3) upon complaint;
(4) while still in service if there is visual
evidence of damage; and
(5)
whenever an approved check, such as the variable burden method in the case of
current transformers, made whenever the meter was tested indicated that a
quantitative test is required.
G.
Generating station meter
tests: Each generating utility may establish its own test procedures to
insure the accuracy of its generating station output watt meter and watt-hour
meters as per Subsection A of 17.9.560.13 and Subsection K of 17.9.560.14
NMAC.
H.
Test procedures and
accuracies: Meters shall be tested at the loads indicated below and
adjusted as close as practicable to zero error when found to exceed the
tolerances prescribed below. The test of any meter shall consist of a
comparison of its accuracy with the accuracy of a standard. The commission will
use the applicable provisions of the latest edition of the American standard
code for electricity meters, ANSI standard C-12, as criteria of accepted good
practice.
(1) Alternating current watt-hour
meters:
|
(a) Shop tests:
|
|
Test Load as Approximate Percentage of Test
Current*
|
Power
Factor
|
Tolerances
|
|
100
|
1.0
|
+1.0%
|
|
10
|
1.0
|
+1.0%
|
|
100
|
0.5
|
+1.5%
|
|
(b) Field Tests:
|
|
100
|
1.0
|
+1.0%
|
|
10
|
1.0
|
+1.0%
|
|
*For meters used with current transformers the
current at heavy load shall be approximately one hundred percent of the
secondary rating of the current transformers and at light load approximately
ten percent of that rating.
|
(2)
Direct current watt-hour meters:
|
Test Load as Approximate
Percentage of Test Current
|
Power
Factor
|
Tolerances
|
|
100
|
+1.5%
|
|
10
|
+1.5%
|
(3)
Demand meters:
(a) Integrated (block interval)
demand meters:
(i) Demand meters which are
direct driven shall be tested at a load point no less than fifty percent of
full scale. Tests shall be continuous for at least one demand interval and
shall be started simultaneously with the demand interval of the demand
meter.
(ii) Demand meters which are
actuated by impulses shall be tested by transmitting enough impulses to cause
the meter to register at a load point no less than fifty percent of full scale.
If an impulse-actuated demand meter is equipped with a device which records the
number of impulses received by the meter, and if there is frequent and accurate
comparison of such record with the number of kilowatt hours registered on the
associated watt-hour meter, then it is not necessary to make a periodic field
test of the demand meter.
(iii)
Demand meters shall be adjusted to indicate zero under no-load conditions and
shall be checked to ascertain that the meter resets to zero.
(iv) Impulse devices associated with demand
meters must be checked for proper operation.
(v) The demand meter shall have an accuracy
of within two percent of full scale.
(vi) The time interval must be accurate
within half a percent for synchronous motor timing elements and within two
percent for mechanical clock timing elements.
(vii) Meters recording demand reading on a
chart which provides a record of the time at which the demand occurs shall be
accurate to within plus or minus four minutes in 24 hours.
(b) Lagged demand meters:
(i) Demand meters shall be tested at a load
point no less than fifty percent of full scale.
(ii) Demand meters shall be adjusted to
indicate zero under no-load conditions with potential applied.
(iii) The demand meter shall have an accuracy
within three percent of full scale.
(iv) Meters recording demand readings on a
chart which provides a record of the time at which the demand occurs shall be
accurate to within plus or minus four minutes in 24 hours.
(4) Transformers:
(a) All current and potential transformers
shall be tested in accordance with the applicable procedures prescribed in ANSI
standard C-57.13.
(b) Any utility
unable to perform the above tests due to a lack of proper equipment may have
its instrument transformers tested by another utility or laboratory whose
testing conforms to the requirements of the commission.
(c) In lieu of the utility testing of
instrument transformers the commission will accept the certificate of test as
furnished by the manufacturer.
(d)
Current or potential transformers shall not be installed if their accuracy does
not fall within the 0.6 accuracy class as described in ANSI standard
C-57.13.
(5) Meters for
measurement of purchased electricity: Utilities purchasing electricity from
non-utilities or from utilities outside the state must see that the instruments
and meters which are necessary to furnish complete and accurate information as
to the energy purchased are installed and tested in accordance with the
requirements of the commission.
(6)
General:
(a) All meters when tested shall be
adjusted as closely as practicable to the condition of zero error.
(b) All tolerances are to be interpreted as
maximum permissible variations from the condition of zero error. In making
adjustments no advantage of the prescribed tolerance limits shall be
taken.
(c) Meters shall not
"creep," i.e., there shall be no continuous rotation of the moving element of a
meter at a speed in excess of one revolution in 10 minutes when the meter load
wires have been removed and voltage is applied to the potential elements of the
meter.
I.
Facilities and equipment for meter testing: Each utility shall
maintain a meter shop or shall have the services of a meter shop available to
it for the purpose of inspecting, testing, and repairing meters. The shop shall
be open for inspection by authorized representatives of the commission at all
reasonable times, and the facilities and equipment as well as the methods of
measurement and testing employed shall be subject to the approval of the
commission. The meter shop used by a utility shall have adequate and sufficient
testing equipment to comply with this rule and to conduct the tests and make
repairs and adjustments in compliance with this rule.
(1) Each location at which the shop conducts
tests of meters shall have a three-phase voltage supply, one phase of which
shall be variable from zero volts to 270 volts.
(2) Standards: Extreme care shall be
exercised in the handling of standards to assure that their accuracy is not
disturbed. Each meter shop shall contain facilities for protected storage of
the secondary standards which are accessible only to personnel specifically so
assigned by the utility management.
(a)
Secondary standards:
(i) Each shop shall have
at least one indicating voltmeter with a stated accuracy within one-quarter
percent of full scale. This instrument must be maintained within its stated
accuracy.
(ii) Each shop shall have
at least one portable rotating standard watt-hour meter with a correction of
not more than one-half percent at commonly used loads. If the correction
percentage varies between successive tests by more than one-quarter percent, a
complete check must be made to determine the cause of such variation. If the
cause of variation cannot be removed the use of the instrument should be
discontinued.
(iii) Secondary
standards shall be checked periodically (See Paragraph (2) of Subsection E of
17.9.560.14 NMAC) at the national bureau of standards or at a laboratory
acceptable to the commission. Secondary standards otherwise shall be kept in
the protected storage of the meter shop at all times.
(iv) Secondary standards 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.
(b) Working standards: Each shop
shall have at least one portable rotating standard watt-hour meter with a
correction of not more than one-half percent at commonly used loads. If the
correction percentage varies between successive tests by more than one-quarter
percent, a complete check must be made to determine the cause of such
variation. If the cause of variation cannot be removed the use of the
instrument should be discontinued. Working standards shall be checked
periodically (See Paragraph (2) of Subsection E of 17.9.560.14 NMAC) by
comparison with a secondary standard from the protected storage of the meter
shop.
J.
Records of meters: Each utility shall maintain records of the
following data, where applicable, for each meter until retirement:
(1) the complete identification (number,
type, voltage, amperes, number of wires, disk constant (kh), demand interval,
and ratio); and
(2) the dates of
installation and removal from service together with the location.
K.
Meter test
records: Each utility shall keep meter test records until a superseding
test has been made but not less than two years or as may be necessary to comply
with service rules regarding refunds on inaccurate meters. Test records shall
include the following:
(1) the date and reason
for the test;
(2) the reading of
the meter before making any test;
(3) the accuracy "as found" at light and
heavy loads;
(4) the accuracy "as
left" at light and heavy loads; and
(5) a statement of any repairs
made.
