Superseded Standard

IEEE C57.91-1981

IEEE Guide for Loading Mineral-Oil-Immersed Overhead and Pad-Mounted Distribution Transformers Rated 500kVA and Less with 65 C or 55 C Average Winding Rise

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
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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Superseded Standard
Superseded by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
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Sponsor Committee
PE/TR - Transformers
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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.

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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.

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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.

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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.

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No Inactive-Withdrawn Standards
No Inactive-Reserved Standards
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