Section 460.3609. Instrument transformers used in conjunction with metering equipment; requirements; phase shifting transformers; secondary voltage.

(1) Instrument transformers used in conjunction with metering equipment to measure a customer's service shall meet both of the following requirements:

(a)   Be in proper mechanical condition and have satisfactory  electrical insulation for the service on which used.

(b)  Have characteristics such that the combined inaccuracies of all transformers supplying 1 or more meters in a given installation will not exceed the percentages listed in the following chart:

100% Power          50%

Factor                    Power Factor

Current	10%	100%	10%	100%
Error 1%	0.75%	3%	2%

(2)   Meters that are used in conjunction with instrument transformers shall be adjusted so that the overall accuracies will come within the  limits specified in this part.

(3)    Instrument transformers shall be tested with the meter with which they are associated by making an overall test or may be checked separately. If the transformers are tested separately, the meters shall also be checked to see that the overall accuracy of the installation  is within the prescribed accuracy requirements. (See R 460.3613 (6).)

(4)   The results of tests of instrument transformers shall be kept on record and shall be available for use.

(5)   Phase shifting transformers shall have secondary  voltages  under balanced line voltage conditions within plus or minus 1.0% of the voltage impressed on the primary side of the transformer.

History: 1983 AACS; 2008 AACS.