IEEE C57.12.91:2020

Revision Standard - Active.
To reflect current practice in the testing procedures of dry-type transformers, substantive changes to Clause 5, Clause 7, Clause 10, Clause 11, and Clause 13 of IEEE Std C57.12.91-2011 have been made in this revision. Also Annex B has been added to provide guidelines for converting test results measured at 60 Hz to the equivalent values at 50 Hz and vice versa. This revision does not address transformer requirements and specific test criteria; rather they are contained in appropriate standards such as IEEE Std C57.12.01 or in user specifications.

This standard describes methods for performing tests specified in IEEE Std C.57.12.01 and other referenced standards applicable to dry-type distribution and power transformers, with a voltage of 601 V or higher in the highest voltage winding.2 It is intended for use as a basis for performance and for the proper testing of dry-type distribution and power transformers. This standard applies to all dry-type transformers including those with solid cast and/or resin encapsulated windings, except as follows:
a) Instrument transformers
b) Step-voltage and induction voltage regulators
c) Arc furnace transformers
d) Rectifier transformers
e) Specialty and General Purpose transformers
f) Mine transformers
g) Testing transformers
h) Welding transformers
The purpose of this standard is to provide information regarding the procedures for the testing of dry-type transformers. Transformer requirements and specific test criteria are not a part of this standard but are contained in appropriate standards such as IEEE Std C57.12.01 or in user specifications.