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.

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December 5, 2001

Interpretation Request #1
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.