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IEEE DRAFT C37.91 : D7.0 2006

Superseded

Superseded

A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.

View Superseded by

PROTECTING POWER TRANSFORMERS

Superseded date

30-05-2008

Superseded by

IEEE C37.91-2008 REDLINE

Published date

12-01-2013

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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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