Provided in this recommended practice are calculation methods for conservatively evaluating the feasibility for an existing installed dry-type or liquid immersed transformer, to supply nonsinusoidal load currents as a portion of the total load. Also provided is necessary application information to assist in properly specifying a new transformer expected to carry a load, a portion of which is composed of nonsinusoidal load currents. A number of examples illustrating these methods and calculations are presented. Reference annexes provide a comparison of the document calculations to calculations found in other industry standards. Suggested temperature rise calculation methods are detailed for reference purposes.

This recommended practice applies only to two winding transformers covered by IEEE Std C57.12.00, IEEE Std C57.12.01, and NEMA ST20.1 It does not apply to rectifier transformers

The purpose of this document is to establish uniform methods for determining the capability of transformers when supplying nonsinusoidal load currents of known characteristics