1、IEEE Std C37.91 -2008 (Revision of IEEE Std C37.91-2000) IEEE Guide for Protecting Power Transformers IEEE 3 Park Avenue New York, NY 10016-5997, USA 30 May 2008 IEEE Power Engineering Society Sponsored by the Power System Relaying Committee C37.91 TMIEEE Std C37.91 -2008 (Revision of IEEE Std C37.9
2、1-2000) IEEE Guide for Protecting Power Transformers Sponsor Power System Relaying Committee of the IEEE Power Engineering Society Approved 31 January 2008 IEEE-SA Standards Board Abstract: This guide is intended to provide protection engineers and other readers with guidelines for protecting three-
3、phase power transformers of more than 5 MVA rated capacity and operating at voltages exceeding 10 kV. In some cases, a user may apply the techniques described in this guide for protecting transformers of less than 5 MVA ratings or operating at voltages less than 10 kV. Information to assist protecti
4、on engineers in applying properly relays and other devices to protect transformers used in transmission and distribution systems is provided in this guide. General philosophy, practical applications, and economic considerations involved in power transformer protection are discussed. Emphasis is plac
5、ed on practical applications. Types of faults in transformers are described. Technical problems with the protection systems, including the behavior of current transformers during system faults, are discussed. Associated problems, such as fault clearing and reenergization, are discussed as well. Keyw
6、ords: analysis of dissolved gases in transformer oil, application of multifunction relays for transformer protection, differential protection, failures of transformers, overcurrent protection, protection of phase-shifting transformers, protection of transformers, volts-per-hertz protection The Insti
7、tute of Electrical and Electronics Engineers, Inc. 3 Park Avenue, New York, NY 10016-5997, USA Copyright 2008 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Published 30 May 2008. Printed in the United States of America. IEEE is a registered trademark in the U.S.
8、 Patent +1 978 750 8400. Permission to photocopy portions of any individual standard for educational classroom use can also be obtained through the Copyright Clearance Center. Introduction This introduction is not part of IEEE Std C37.91-2008, IEEE Guide for Protecting Power Transformers. This docum
9、ent is a revision of IEEE Std C37.91 -2000, IEEE Guide for Protective Relay Applications to Power Transformers. This guide is intended to provide aid in the effective application of relays and other devices for the protection of power transformers. In this revision, several areas have been improved.
10、 Most notably: Several clauses have been revised. Differential protection has been augmented to include the techniques used in numerical relays. Techniques now being used in numerical relays, such as harmonic restraint and harmonic blocking, wave shape recognition, low-current detection, and direct-
11、current blocking methods, are included. An example of the relay blocking logic is included. New figures have been included to reflect the practice of connecting all current transformers (CTs) in wye configuration when numerical relays are used. The possibility of CT saturation when faults occur outs
12、ide the protection zone of differential relays and the current does not flow through the differential zone is explained. Protection of transformers for faults in the grounded wye-connected windings has been expanded to include the use of restricted earth-fault relays. The practice of remote tripping
13、 of circuit breakers to protect transformers used to tap transmission and subtransmission lines is explained. The clause on gas analysis has been revised to bring it in line with the current practices. The use of rate of change of total dissolved combustible gases is incorporated. New annexes have b
14、een created. Annex B lists the transformer failure statistics collected by the Canadian Electrical Association. Annex C outlines the procedure for setting relays for protecting three transformers. The first transformer is a step-up transformer, the second transformer is a network autotransformer, an
15、d the third transformer is used for supplying energy to a distribution system. Annex D describes the need for monitoring current on the high-voltage and low-voltage windings, when automatic tap changing is used, for determining the hot-spot temperature of a transformer. Annex E outlines the methods
16、that are used in differential relays for compensating for the phase shift in delta-wye transformers. Notice to users Laws and regulations Users of these documents should consult all applicable laws and regulations. Compliance with the provisions of this standard does not imply compliance to any appl
17、icable regulatory requirements. Implementers of the standard are responsible for observing or referring to the applicable regulatory requirements. IEEE does not, by the publication of its standards, intend to urge action that is not in compliance with applicable laws, and these documents may not be construed as doing so. iv Copyright 2008 IEEE. All rights reserved.
