IEEE C37.91 2008

$46.04

IEEE Guide for Protecting Power Transformers

Published By	Publication Date	Number of Pages
IEEE	2008	151

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Description

Revision Standard – Active. Revision of IEEE Std C37.91-2000. This guide is intended to provide protection engineers and 1 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.

PDF Catalog

PDF Pages	PDF Title
1	IEEE Std C37.91-2008 Front cover
3	Title page
6	Introduction Notice to users Laws and regulations
7	Copyrights Updating of IEEE documents Errata Interpretations Patents
8	Participants
10	Contents
13	Important notice 1. Overview 1.1 Scope 1.2 Purpose 2. Normative references
14	3. Definitions
15	4. Device numbers 5. Philosophy and economic considerations
16	6. Types of failures in transformers
17	7. Relay currents 7.1 Minimum internal faults
18	7.2 Maximum internal faults 7.3 Performance of current transformers
20	7.4 Reasons for mismatch
22	8. Electrical detection of faults
23	8.1 Fuse protection and self-powered resettable fault interrupters
24	8.2 Differential protection
41	8.3 Overcurrent relay protection
43	8.4 Ground-fault protection
48	8.5 Fault detection for special-purpose transformers
53	8.6 Backup and external fault protection
55	8.7 Temperature relays
56	8.8 Miscellaneous relays 9. Mechanical detection of faults 9.1 Gas accumulator relay 9.2 Gas detector relay
57	9.3 Pressure relays
59	10. Thermal detection of abnormalities 10.1 Thermal relays for winding temperature
61	10.2 Other means of thermal protection
63	11. Fault clearing
64	11.1 Relay tripping circuits 11.2 Circuit breakers 11.3 Tripping of remote circuit breakers
66	11.4 Circuit switcher 11.5 Fuses
67	11.6 Self-powered resettable fault interrupters 12. Reenergizing practice
68	13. Gas analysis
69	13.1 Level of TDCG and rate of change of TDCG approach
70	13.2 Ratio of gases approach
71	14. Special protective schemes 14.1 Overall unit generator differential
73	14.2 Unit transformer of three-legged core form type 14.3 Grounding transformer inside the main transformer differential zone
74	14.4 Unbalanced voltage protection for wye-connected, three-legged, core-type transformers
75	14.5 Differential protection of single-phase transformers connected in three-phase banks
77	14.6 Differential protection of a bank of three single-phase autotransformers with delta tertiary
78	14.7 Differential protection of single-phase transformers in a three-phase bank with a spare transformer
79	15. Other considerations
80	Annex A (informative) Application of the transformer through-fault-current duration guide to the protection of power transformers