Current through September 24, 2024
(1) General
In-Service performance tests must be made in accordance with Rules
1220-4-4-.35(2), 1220-4-4-.35(3), or 1220-4-4-.35(4). These tests may be made
on the customer's premises or in the utility's meter shop. However, it is
recommended that meters associated with instrument transformers, or phase
shifting transformers, or those having mechanical contact devices, be tested on
the customer's premises. Tests made for other purposes, such as request tests
or referee tests, must not be counted as in-service performance tests. All
meters on a utility's system must be tested in accordance with a single
program, which must be one of the following:
(a) At a fixed periodic interval in
accordance with 1220-4-4-.35(2).
(b) At a variable interval in accordance with
1220-4-4-.35(3).
(c) An acceptable
statistical sampling program in accordance with 1220-4-4-.35(4).
(2) Periodic Test Schedule
If this option is used, the basic periodic test interval for
meters shall not be longer than provided for in American National Standard for
Electric Meters - ANSI C 12.1, latest edition, and as follows for secondary
standards:
(a) Portable electronic
watt-hour standards
..................................................................................
yearly
(b) Indicating voltmeters
..............................................................................................................
yearly
(c) Instrument transformer
standards
....................................................................................
as required
(3) Variable
Interval Plan
(a) If this option is used, the
variable interval plan shall conform to American National Standard for Electric
Meters - ANSI C 12.1, latest edition, for all meters that do not have an
additional mechanical attachment such as a thermal or mechanical
register.
(b) The variable interval
plan shall be accompanied by an adequate policy for testing meters on request
and a procedure whereby unusually high or low bills for service would be
detected and investigated.
(4) Statistical Sampling
(a) If this option is used, the statistical
sampling plan shall conform to American National Standard for Electric Meters -
ANSI C 12.1, latest edition, and shall use American Standard for Quality
Control, ANSI, ASQCZ1.9, latest edition, to select sample quantities and to
analyze test results, for all meters that do not have an additional mechanical
attachment such as a thermal or mechanical register.
(b) A statistical sampling program shall
included an adequate policy for testing meters on request and a procedure
whereby unusually high or low bills for service would be detected and
investigated.
(c) An acceptable
sampling plan is one in which a sample will, ninety-five (95) times out of one
hundred (100), correctly identify a homogenous group of meters, which has at
least ninety-seven and one half percent (97.5%) of the group within the limits
ninety-eight percent to one hundred two percent (98% - 102%) registration on
in-service performance test. If a group of meters does not meet acceptable
performance criteria, then corrective action must be taken.
(d) The corrective action may consist of an
accelerated test program to raise the accuracy performance of the group from
service. An accelerated test program should provide for testing at rates that
vary in accordance with the calculated percentage of defective meters in
rejected groups. In its application to an individual group the rate of testing
should be such that the required corrective action is completed in four (4)
years, but not more than twenty-five percent (25%) of the meters in the group
need to be tested in any one (1) year. Accelerated testing may be discontinued
when the test results indicate that the rejected group is within acceptable
limits.
(e) Records shall be
maintained and tabulated to indicate the number of meters in each homogeneous
group in service at the beginning of each year, the number of meters making up
the sample for each homogeneous group, the test results for each group, and any
necessary corrective action taken.
Authority: T.C.A. §
65-2-102.
