Wisconsin Administrative Code › Public Service Commission › Chapter PSC 113 - Service Rules For Electrical Utilities › Subchapter IX - Electric Meter Testing Programs and Record Requirements › Section PSC 113.0921 - Statistical sample testing plan for in-service, electronic (solid state) meters and electromechanical, self-contained, single phase and 3-wire network meters

Current through June 24, 2024
(1) The statistical sample testing plan
				described in pars. (a) to (e) may be used for testing electronic (solid state)
				meters and self-contained, single phase and 3-wire network meters without
				mechanical demand registers or mechanical pulsing devices in place of the
				periodic testing requirements of s.
				PSC
				113.0911 if the commission authorizes the adoption of
				the plan by a utility.
(a) All extended
				range, surge proof designed meters shall be divided into homogeneous groups
				based on meter design features and age. The groups shall be further divided
				into lot sizes categorized by manufacturer, type, serial number, group size or
				load duty cycle with lot sizes containing a minimum of 26 meters and a maximum
				of 110,000 meters. The number of lots or lot composition and size may be
				changed at the end of the sample testing year to allow for increasing or
				decreasing analysis of accuracy testing requirements on any segment of meters
				in any lot.
(b) Annually, from each
				of the assembled lots, a coded sample size specified in Table A-2, Inspection
				Level IV, page 4 of Military Standard 414, (MIL-STD-414) dated 11 June 1957 and
				a corresponding actual sample size as shown on Table B-3 page 45,
				(MIL-STD-414), shall be randomly selected for testing and analysis purposes.
				Each meter in the lot sample shall be provided with a full load and light load
				test for accuracy at unity power factor, as specified under s. . A separate
				statistical analysis shall be performed on each lot sample at each of these 2
				load ranges. All meters not registering at either full or light load test
				points shall be removed from the lot sample and replaced with a different
				randomly selected meter and not more than two lot sample meters operating
				outside of the accuracy bandwidth of 95% to 105% at either test load point
				shall be removed and replaced from the lot sample.
(c) The statistical analysis calculations for
				both the full and light load accuracy results from the sample lot tests shall
				be made following the example outlined on page 43 of MIL-STD-414 with the upper
				and lower specification limits, U and L designated at 102% and 98%
				respectively. The test criterion for acceptance or rejection of each lot shall
				be by the Standard Deviation Method, Double Specification Limit with an
				Acceptable Quality Level (AQL) of 1.00 for the full load analysis and 4.00 for
				the light load analysis (both normal inspection) as shown on Table B-3, page 45
				of MIL-STD-414.
(d) A lot shall be
				deemed acceptable for continued use if the total estimated percent defective
				(P) is less than the appropriate maximum allowable percent defective (M) as
				determined from Table B-3, page 45 of MIL-STD-414, following the procedure of
				par. (c) for both the full load and light load analysis test points at the
				respective designated Acceptable Quality Levels. All of the meters in the
				accepted lot may be retained in use without further accuracy adjustments and
				will be concluded to have the accuracy characteristics specified in s.
				PSC 113.0811(1)
				(c). Meters in the sample lot may be adjusted
				for acceptable accuracy as required or maintained as necessary and returned to
				the lot.
(e) A lot shall be deemed
				unacceptable and rejected for continued use if the total estimated percent
				defective (P) is greater than or equal to the appropriate maximum allowable
				percent defective (M) as determined from Table B-3, page 45 MIL-STD-414,
				following the procedure of par. (c) for both the full load and light load
				analysis test points at the respective designated Acceptable Quality Levels on
				any 2 annual sample testing analysis years within a five-year period for the
				lot or any meters in the lot. All meters in a rejected lot shall be provided
				with an appropriate test within a period of 48 months from the date of
				completion of the sample analysis and all the meters tested in the rejected lot
				shall be adjusted to the accuracies specified in s.
				PSC 113.0811(1)
				(c). All meters in a rejected lot that will
				not be returned to service shall be removed within 48 months from the date of
				completion of the sample analysis. These meters may be retired without a test.
				Annual statistical sample testing shall be terminated during the period when
				all of the meters in a rejected lot are being provided with a test and accuracy
				adjustment.
(f) All meters in any
				lot may be tested and adjusted for proper accuracy over a 48-month period at
				the discretion of the utility without a sample analysis determination
				specifying the lot test is necessary.
(g) Any meter that is included in this plan,
				which is removed from service for retirement, may be retired without a
				test.