Active PAR

IEEE PC57.91

IEEE Draft Guide for Loading Mineral-Oil-Immersed Transformers and Step-Voltage Regulators

The contents of this guide describe the assumptions, techniques, and methods for estimating the effects of loading above nameplate of mineral-oil-immersed distribution and power transformers as well as step voltage regulators. Consequences due to loading above nameplate ratings are discussed including damage to insulation, production of gases in oil, and ultimately loss of life effects. In addition, effects of loading on auxiliary equipment are presented. Different types of loading scenarios as well as variations in ambient temperature and altitude are described. Effects due to different cooling techniques and their impacts on transformer capacity are reviewed. Transformer temperature criteria are also provided. Finally, calculation methods with and without consideration to duct oil effects are provided and with sample temperature calculations.

Sponsor Committee
PE/TR - Transformers
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Status
Active PAR
PAR Approval
2017-09-28
Superseding
C57.91-2011
Open Source
IEEE SA Open Source Project
Open Source CLA
BSD 3-Clause

Working Group Details

Society
IEEE Power and Energy Society
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Sponsor Committee
PE/TR - Transformers
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Working Group
WGC57.91 - Insulation Life - Loading Guide Working Group
IEEE Program Manager
Patrycja Jarosz
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Working Group Chair
David Wallach

Other Activities From This Working Group

Current projects that have been authorized by the IEEE SA Standards Board to develop a standard.


No Active Projects

Standards approved by the IEEE SA Standards Board that are within the 10-year lifecycle.


No Active Standards

These standards have been replaced with a revised version of the standard, or by a compilation of the original active standard and all its existing amendments, corrigenda, and errata.


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.

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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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These standards have been removed from active status through a ballot where the standard is made inactive as a consensus decision of a balloting group.


No Inactive-Withdrawn Standards

These standards are removed from active status through an administrative process for standards that have not undergone a revision process within 10 years.


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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