Section 1220-04-04-.35 - IN-SERVICE PERFORMANCE TESTS(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.Tenn. Comp. R. & Regs. 1220-04-04-.35
Original rule certified May 9, 1974. Amendment filed October 30, 2000; effective January 13, 2001.Authority: T.C.A. § 65-2-102.