Section PSC 113.0813 - Requirements for instrument transformers(1) Instrument transformers used in conjunction with metering equipment to measure customers' service shall: (a) Be in proper mechanical condition and have electrical insulation satisfactory for the service used.(b) Be 0.3% accuracy-class units and otherwise have characteristics such that the combined inaccuracies of all transformers supplying one or more meters in a given installation will not exceed the total accuracies for the following conditions: 1. Power factor equals 1.0 and 10% load, accuracy equals 0.6%.2. Power factor equals 1.0 and 100% load, accuracy equals 0.3%.3. Power factor equals 0.5 and 100% load, accuracy equals 1.0%.(2)(a) Meters used in conjunction with instrument transformers shall be adjusted so that the overall accuracies will come within the limits specified ss. PSC 113.0811 and 113.0812.(b) 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.(c) The results of tests of instrument transformers shall be kept on record and available for use when transformers are installed. For other than 0.3 % accuracy class instrument transformers, the results of the most recent test for each instrument transformer shall be entered on or attached to the test card form for each test of the associated meter prior to the test of that meter.(3) Phase shifting transformers shall have secondary voltages under balanced line-voltage conditions within 1% plus or minus of the voltage impressed on the primary.Wis. Admin. Code Public Service Commission PSC 113.0813
CR Register, July, 2000, No. 535, eff. 8-1-00.