Superseded Standard

IEEE C37.91-2008

IEEE Guide for Protecting Power Transformers

Revision of IEEE Std C37.91-2000. This guide is intended to provide protection engineers and other readers with guidelines for protecting three-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. The guide provides information to assist protection engineers in applying properly relays and other devices to protect transformers used in transmission and distribution systems. General philosophy, practical applications, and economic considerations involved in power transformer protection are discussed. Emphasis is placed on practical applications. Types of faults in transformers are described. Technical problems with the protection systems, including the behavior of current transformers (CTs) during system faults, are discussed. Associated problems, such as fault clearing and re-energization, are discussed as well.

Sponsor Committee
PE/PSRCC - Power System Relaying and Control
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Status
Superseded Standard
PAR Approval
2007-12-05
Superseded by
C37.91-2021
Superseding
C37.91-2000
Board Approval
2008-01-31
History
ANSI Approved:
2008-06-12
Published:
2008-05-30

Working Group Details

Society
IEEE Power and Energy Society
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Sponsor Committee
PE/PSRCC - Power System Relaying and Control
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Working Group
C37.91_WG-K16 - Protecting Power Transformers Working Group
IEEE Program Manager
Malia Zaman
Contact
Working Group Chair
William English
No Active Projects

C37.91-2021

IEEE Guide for Protecting Power Transformers

Guidelines for protecting three-phase power transformers of more than 5 MVA rated capacity and operating at voltages exceeding 10 kV is provided to protection engineers and other readers in this guide. 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 protection engineers in properly applying relays and other devices to protect transformers used in transmission and distribution systems is also provided. General philosophy, practical applications, and economic considerations involved in power transformer protection are discussed, with an emphasis 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, as well as associated problems, such as fault clearing and post trip reenergization.

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No Superseded Standards
No Inactive-Withdrawn Standards
No Inactive-Reserved Standards
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