IEEE DRAFT C37.91 : D7.0 2006
Superseded
A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.
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PROTECTING POWER TRANSFORMERS
05-30-2008
01-12-2013
1 Overview
1.1 Scope
1.2 Purpose
2 Normative references
3 Definitions
4 Device Numbers
5 Philosophy and economic considerations
6 Types of failures in transformers
7 Relay currents
7.1 Minimum internal faults
7.2 Maximum internal faults
7.3 Through faults
7.4 Performance of CTs
7.5 Reasons for mismatch
8 Electrical detection of faults
8.1 Fuse protection and self-powered re-settable fault
interrupters
8.2 Differential protection
8.3 Overcurrent relay protection
8.4 Ground fault protection
8.5 Fault detection for special purpose transformers
8.6 Backup and external fault protection
8.7 Temperature relays
8.8 Miscellaneous relays
9 Mechanical detection of faults
9.1 Gas accumulator relay
9.2 Gas detector relay
9.3 Pressure relays
10 Thermal detection of abnormalities
10.1 Thermal relays for winding temperature
10.2 Other means of thermal protection
10.3 Testing thermal relays
11 Fault clearing
11.1 Relay tripping circuits
11.2 Circuit breakers
11.3 Tripping of remote circuit breakers
11.4 Circuit switcher
11.5 Fuses
11.6 Self-powered re-settable fault interrupters
12 Re-energizing practice
13 Gas analysis
14 Special protective schemes
14.1 Overall unit generator differential
14.2 Unit transformer of three legged core form type
14.3 Grounding transformer inside the main transformer
differential zone
14.4 Unbalanced voltage protection for wye connected three
legged core type transformers
14.5 Differential protection of single-phase transformers
connected in three-phase banks
14.6 Differential protection of a bank of three single
phase autotransformers with delta tertiary
14.7 Differential protection of single-phase transformers
in a three-phase bank with a spare transformer
15 Other considerations
Annex A (informative) Application of the transformer
through-fault current duration guide to the protection
of power transformers
Annex B (informative) Transformer failure statistics
Annex C (informative) Examples of setting transformer protection
relays
C.1 Electromechanical relays for protecting a step up
transformer
C.2 Setting relays for a network autotransformer
C.3 Relay settings for a distribution transformer
Annex D (informative) Thermal overload protection
D.1 General theory
D.2 Winding temperature monitoring on transformer with OLTC
D.3 Limitations of traditional winding temperature indicator
D.4 Protection
D.5 Digital relays for transformer thermal winding protection
D.6 Measuring temperature with imbedded RTD sensors
Annex E (informative) Internal phase shift and zero sequence
compensation in numerical relays
E.1 An example
E.2 Reasons for using internal compensation
E.3 Differential current compensation connections
E.4 Examples
Annex F (informative) BIBLIOGRAPHY
Annex G (informative) Additional sources of information
G.1 General information
G.2 Fault detection
G.3 Pressure and gas analysis
G.4 Overvoltage
Presents general philosophy, practical applications, and economic considerations involved in power transformer protection.
| DocumentType |
Draft
|
| PublisherName |
Institute of Electrical & Electronics Engineers
|
| Status |
Superseded
|
| SupersededBy |
| IEEE C37.108-2002 | IEEE Guide for the Protection of Network Transformers |
| IEEE C37.102-2006 REDLINE | IEEE Guide for AC Generator Protection |
| IEEE C37.112-1996 | IEEE Standard Inverse-Time Characteristic Equations for Overcurrent Relays |
| IEEE C57.12.01-2015 REDLINE | IEEE Standard for General Requirements for Dry-Type Distribution and Power Transformers |
| IEEE C57.13.3-2014 | IEEE Guide for Grounding of Instrument Transformer Secondary Circuits and Cases |
| IEC 60599:2015 | Mineral oil-filled electrical equipment in service - Guidance on the interpretation of dissolved and free gases analysis |
| IEEE C57.12.00-2015 | IEEE Standard for General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers |
| IEEE C57.91-2011 REDLINE | IEEE Guide for Loading Mineral-Oil-Immersed Transformers and Step-Voltage Regulators |
| IEEE C57.12.90-2010 | IEEE Standard Test Code for Liquid-Immersed Distribution, Power, and Regulating Transformers |
| IEEE C57.104-2008 | IEEE Guide for the Interpretation of Gases Generated in Oil-Immersed Transformers |
| IEEE 242-2001 | IEEE Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems (IEEE Buff Book) |
| IEEE C37.119-2005 | IEEE Guide for Breaker Failure Protection of Power Circuit Breakers |
| IEEE C2-2017 | NATIONAL ELECTRICAL SAFETY CODE (NESC)(R) |
| IEEE C37.40-2003 | IEEE Standard Service Conditions and Definitions for High-Voltage Fuses, Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and Accessories |
| IEEE C57.92-1981 | IEEE Guide for Loading Mineral-Oil-Immersed Power Transformers Up to and Including 100 MVA with 55 C or 65 C Average Winding Rise |
| IEEE 142 : 2007 | GROUNDING OF INDUSTRIAL AND COMMERCIAL POWER SYSTEMS |
| IEEE C57.109-1993 | IEEE Guide for Liquid-Immersed Transformers Through-Fault-Current Duration |
| NFPA 70 : 2017 | NATIONAL ELECTRICAL CODE |
| IEEE C37.103-2015 | IEEE Guide for Differential and Polarizing Relay Circuit Testing |
| IEEE C57.12.91-2011 | IEEE Standard Test Code for Dry-Type Distribution and Power Transformers |
| IEEE C37.113-1999 | IEEE Guide for Protective Relay Applications to Transmission Lines |
| IEEE C57.110-2008 REDLINE | IEEE Recommended Practice for Establishing Liquid-Filled and Dry-Type Power and Distribution Transformer Capability When Supplying Nonsinusoidal Load Currents |
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