Interpretations

Answering questions that may arise related to the meaning of portions of an IEEE standard concerning specific applications.

IEEE Standards Interpretation for IEEE Std C57.91™-1995 IEEE Guide for Loading Mineral-Oil-Immersed Transformers

Copyright © 2001 by the Institute of Electrical and Electronics Engineers, Inc. 3 Park Avenue New York, New York 10016-5997 USA All Rights Reserved.

Interpretations are issued to explain and clarify the intent of a standard and do not constitute an alteration to the original standard. In addition, interpretations are not intended to supply consulting information. Permission is hereby granted to download and print one copy of this document. Individuals seeking permission to reproduce and/or distribute this document in its entirety or portions of this document must contact the IEEE Standards Department for the appropriate license. Use of the information contained in this document is at your own risk.

IEEE Standards Department Copyrights and Permissions 445 Hoes Lane, Piscataway, New Jersey 08855-1331, USA

December 5, 2001

Interpretation Request #1
Topic:
Error in Note "a" of Table 8 Relevant Clause: Table 8; subclause 9.3.1

In IEEE Std C57.91-1995, IEEE Guide for Loading Mineral-Oil-Immersed Transformers, Note "a" of Table 8 reads 110 degrees C. This is incorrect. Is the allowed continuous temperature 110 degrees C or is it 100 degrees C?

Interpretation Response
There is an error in Note "a" of Table 8. IEEE has recently sent out an Invitation to Ballot for a corrigenda to C57.12.91. It includes corrections to several portions of the document. When the corrigenda is approved, Note "a" of Table 8 will be corrected to say 110 degrees C, rather than the 100 degrees C.

Clause 9.3.1 explains that the requirements for loading are in C57.12.00™-2000, IEEE Trial-Use General Requirements and Test Code for Dry-Type and Oil-Immersed Smoothing Reactors for DC Power Transmission. It also states that the continuous operation limit for the hottest-spot temperature is 110 degrees C.