General recommendations for loading 65 degrees Centigrade-rise mineral-oil-immersed overhead and pad-mounted distribution transformers are covered. Recommendations for 55 degrees Centigrade-rise transformers are included because a substantial percentage of these transformers are still in service. The recommendations are based on winding hottest-spot calculations only. Other factors that may limit the permissible load to lower values are listed. A method to establish winding temperature and loss of life by nomographs is given.
- Sponsor Committee
- PE/TR - Transformers
Learn More - Status
- Superseded Standard
- Superseded by
- C57.91-1995
- Board Approval
- 1979-03-15
- History
-
- ANSI Approved:
- 1992-01-13
- Published:
- 1981-07-31
- Reaffirmed:
- 1991-03-21
Working Group Details
- Society
- IEEE Power and Energy Society
Learn More - Sponsor Committee
- PE/TR - Transformers
Learn More - Working Group
-
InsLife-WGC57.91 - Insulating Life - Loading Guide Working Group
- IEEE Program Manager
- Malia Zaman
Contact - Working Group Chair
- David Wallach
PC57.91
Guide for Loading Mineral-Oil-Immersed Transformers and Step-Voltage Regulators
This guide provides recommendations for loading mineral-oil-immersed transformers and step-voltage regulators with insulation systems rated for a 65 u00b0C average winding temperature rise at rated load. This guide applies to transformers manufactured in accordance with IEEE Std C57.12.00 and tested in accordance with IEEE Std C57.12.90, and step-voltage regulators manufactured and tested in accordance with IEEE Std C57.15. Because a substantial population of transformers and step-voltage regulators with insulation systems rated for 55 u00b0C average winding temperature rise at rated load are still in service, recommendations that are specific to this equipment are also included.
C57.91-2011
IEEE Guide for Loading Mineral-Oil-Immersed Transformers and Step-Voltage Regulators
This guide provides recommendations for loading mineral-oil-immersed transformers and step-voltage regulators with insulation systems rated for a 65 u00b0C average winding temperature rise at rated load. This guide applies to transformers manufactured in accordance with IEEE Std C57.12.001 and tested in accordance with IEEE Std C57.12.90, and step-voltage regulators manufactured and tested in accordance with IEEE Std C57.15. Because a substantial population of transformers and step-voltage regulators with insulation systems rated for 55 u00b0C average winding temperature rise at rated load are still in service, recommendations that are specific to this equipment are also included.
C57.91-1995
IEEE Guide for Loading Mineral-Oil-Immersed Transformers
General recommendations for loading 65 C rise mineral-oil-immersed distribution and power transformers are covered.
C57.91-1995/Cor 1-2002
IEEE Guide for Loading Mineral-Oil-Immersed Transformers - Corrigendum 1
Errors identified in IEEE Std C57.91-1995 are addressed in this corrigendum.
No Inactive-Withdrawn Standards
No Inactive-Reserved Standards