Section PSC 113.0916 - Testing of instrument transformers(1) No instrument transformer shall be placed in service, or allowed to remain in service, if it shows evidence of physical damage, discolored terminals due to overload, change in texture or resiliency of insulation, or arc tracking on the insulation or bushings.(2) Instrument transformers of all utilities shall be tested for voltage withstand by the manufacturer, the utility, or a laboratory approved for such test by the commission before being placed in service. Each instrument transformer that has been removed from service shall be tested for voltage withstand prior to reinstallation if the reason for removal or physical appearance, gives cause to doubt its reliability. The utility shall maintain a record of all such tests.(3) Instrument transformers of class A privately-owned utilities shall be tested at the utility meter shop or the manufacturers' certified test reports may be used to determine accuracy (ratio correction factor and phase angle):(a) Before being initially placed in service.(b) When removed from service.(c) When there is evidence from outward appearance or performance to suspect inaccuracy.(d) The manufacturer's calibration results may be acceptable on all new voltage transformers rated above 15,000 volts. Removal tests of these transformers may also be omitted except in those cases where there is reason to suspect that a transformer malfunction has occurred.(4) Instrument transformers of other than class A private-owned utilities shall be tested at the utilities meter shop, the manufacturer's laboratory or a laboratory approved by the commission for accuracy (ratio correction factor and phase angle): (a) Before being initially placed in service.(b) When there is evidence from outward appearance or performance to suspect inaccuracy.(5) Instrument transformers in service shall be given an approved check (such as the variable burden method in the case of current transformers or a field check of the secondary voltage with a good quality voltmeter in the case of voltage transformers) made in conjunction with each field test of the associated watthour meter. When such check provides evidence that the instrument transformer may be inaccurate, that instrument transformer shall be tested for accuracy.Wis. Admin. Code Public Service Commission § PSC 113.0916
CR Register, July, 2000, No. 535, eff. 8-1-00.