Legal authority and framework
- The ERC promulgated the amendments pursuant to Section 16(d), (e), (f), and (g) and Section 17(d) of Commonwealth Act No. 146, as amended, and Commonwealth Act No. 349.
- The amendments modify the existing Rules and Procedures for the Test and Maintenance of Electric Meters of Distribution Utilities adopted in ERC Resolution No. 12, series of 2009.
Purpose and regulatory intent
- The amendments modify the existing criteria for acceptance or rejection of sample lots applicable to acceptance testing.
- The amendments establish the instances when Normal, Reduced, and Tightened inspections apply and how switching occurs among these inspection modes (Section 5.4).
- The amendments implement the regulatory requirement of testing meters in service once every two years (Section 6.1).
Scope: acceptance and in-service meters
- Section 5.3 applies to all new and reconditioned or repaired meters referred to the ERC for acceptance testing.
- Acceptance testing uses statistical sampling by attributes based on ANSI Z1.4-1993 with an AQL of 1%.
- Section 6.1 applies to all individual meters in service for periodic testing through a statistical sampling program.
- In-service tests must be conducted once every two-year period after installation (Section 6.1).
- In-service sampling uses ANSI Z1.4-1993 with an Inspection level “General II” and an Acceptability Quality Level (AQL) of 2.5%.
Acceptance testing: Section 5.3 criteria
- All meters for acceptance testing must be sample tested by the ERC using ANSI Z1.4-1993, “Sampling Procedures and Tables for Inspection by Attributes.”
- An Acceptable Quality Level (AQL) of one percent (1%) must be achieved for acceptance testing.
- Single sampling must be performed in one of the three inspections—Normal, Reduced, or Tightened—as shown in Tables 1, 2, and 3.
- Unless otherwise required by the ERC, Normal inspection is used.
- Normal Inspection (Table-1) sets the lot rejection/acceptance thresholds by lot size and sample size, using the following acceptance/rejection criteria for number of non-conforming meters:
- Up to 150: sample 20; accept if 0; reject if 1.
- 151 to 280: sample 32; accept if 1; reject if 2.
- 281 to 500: sample 50; accept if 1; reject if 2.
- 501 to 1,200: sample 80; accept if 2; reject if 3.
- 1,201 to 3,200: sample 125; accept if 3; reject if 4.
- 3,201 to 10,000: sample 200; accept if 5; reject if 6.
- Reduced Inspection (Table-2) sets thresholds as follows:
- Up to 150: sample 13; accept if 0; reject if 2.
- 151 to 280: sample 20; accept if 0; reject if 2.
- 281 to 500: sample 32; accept if 1; reject if 3.
- 501 to 1,200: sample 50; accept if 1; reject if 4.
- 1,201 to 3,200: sample 80; accept if 2; reject if 5.
- 3,201 to 10,000: sample 125; accept if 3; reject if 6.
- Reduced Inspection revert rule (Table-2 note): if the number of non-conforming meters exceeds the criterion for acceptance but is less than the criterion for rejection, the lot is accepted but inspection reverts back to Normal in succeeding lots.
- Tightened Inspection (Table-3) sets thresholds as follows:
- Up to 150: sample 32; accept if 0; reject if 1.
- 151 to 280: sample 50; accept if 0; reject if 1.
- 281 to 500: sample 80; accept if 0; reject if 1.
- 501 to 1,200: sample 125; accept if 1; reject if 2.
- 1,201 to 3,200: sample 200; accept if 2; reject if 3.
- 3,201 to 10,000: sample 315; accept if 3; reject if 4.
Switching inspection levels: Section 5.4
- Switching among Normal, Reduced, and Tightened inspections follows the conditions in Section 5.4.1 to 5.4.4.
- Normal to Reduced (Section 5.4.1): Reduced inspection is instituted while Normal is in effect if either condition occurs:
- After ten (10) consecutive field assignments of acceptance testing with less than five-day duration per assignment in a particular Meter Shop, the ERC authorized representative has found no non-conforming meters in every sample tested lots; or
- After a field assignment of acceptance testing with five-day duration in a particular Meter Shop, the ERC authorized representative has found no non-conforming meters in every sample tested lots.
- Reduced to Normal (Section 5.4.2): While Reduced inspection is in effect, if a lot’s non-conforming count exceeds the criterion for acceptance but is less than the criterion for rejection, the lot is accepted and the ERC authorized representative reverts to Normal inspection in succeeding lots.
- Normal to Tightened (Section 5.4.3): Tightened inspection is instituted while Normal is in effect if either condition occurs:
- After five (5) consecutive field assignments of acceptance testing with less than five-day duration per assignment in a particular Meter Shop, the ERC authorized representative has found two (2) failed lots in the sample-tested lots; or
- After a field assignment of acceptance testing with five-day duration in a particular Meter Shop, the ERC authorized representative has found two (2) failed lots in the sample-tested lots.
- Tightened to Normal (Section 5.4.4): Normal inspection is instituted while Tightened inspection is in effect if either condition occurs:
- After ten (10) consecutive field assignments of acceptance testing with less than five-day duration per assignment in a particular Meter Shop, the ERC authorized representative has found all the sample-tested lots acceptable; or
- After a field assignment of acceptance testing with five-day duration in a particular Meter Shop, the ERC authorized representative has found all sample-tested lots acceptable.
In-service testing program: Section 6.1
- A statistical sampling program must be used to comply with the regulatory requirement of periodic testing of all individual meters in service (Section 6.1).
- Tests must be made once every two-year period after installation.
- The statistical sampling program must conform to ANSI Z1.4-1993 as the basis for random statistical quality control and random sample selection of meters.
- The plan must use Inspection level “General II” Normal and must achieve an AQL of 2.5%.
- In-service testing must use double sampling under Table-4, which prescribes lot size ranges, sample testing series, sample sizes, and acceptance/rejection criteria.
- Double sampling framework (Table-4):
- For lot size Up to 500: first sample size 32; accept if 1 or fewer non-conforming meters and reject if 4 or more; if criteria require a second sample, second sample is 32/50/… per table (as shown) with specified second-sample nonconforming thresholds.
- For lot size 501 to 1,200: first sample size 50; accept if 2; reject if 5; second sample size 50 with acceptance/rejection criteria shown in the table.
- For lot size 1,201 to 3,200: first sample size 80; accept if 3; reject if 7; second sample size 80 with acceptance/rejection criteria shown.
- For lot size 3,201 to 10,000: first sample size 125; accept if 5; reject if 9; second sample size 125 with acceptance/rejection criteria shown.
- For lot size 10,001 to 35,000: first sample size 200; accept if 7; reject if 11; second sample size 200 with acceptance/rejection criteria shown.
- For lot size 35,001 to 150,000: first sample size 315; accept if 11; reject if 16; second sample size 315 with acceptance/rejection criteria shown.
- Meters in lots with sizes of 32 meters and below must be tested individually (Table-4 notes).
- Spare meters may be randomly drawn from the list of meters belonging to the same lot and are governed by Table-4’s spare meters column.
- Spare meters are allowed for replacement only under these stipulated circumstances:
- When the provided number of spare meters is insufficient to replace sample meters found to be either damaged, defective, or tampered;
- When the sample meter is installed in a residence and, at the time of removal for sample testing, the registered customer or his/her representative is not present;
- When the sample meter is installed in a residence with a permanent occupant who is dependent on a life support system that requires electricity; or
- When the sample meter is no longer on site during the conduct of in-service testing.
- Table-4 defines columns for administration of the testing plan, including:
- the number of meters in a lot (Lot size),
- the series number of sample testing,
- sample size,
- maximum number of non-conforming meters to allow acceptance of the lot,
- number of non-conforming meters in sample to cause rejection of the lot,
- criterion triggering the required second sample,
- and the number of randomly selected meters as replacements.
Effect, supersession, and severability
- All portions of the prior rules that are not expressly revised remain in force and effect (Section 2).
- If any amendment is declared unconstitutional or invalid, the other provisions not affected remain in force and effect (Section 3).
- The amendments take effect fifteen (15) days after publication in a newspaper of general circulation in the country (Section 4).