Project Details
This guide provides recommendations for loading mineral-oil-immersed transformers and step-voltage regulators with insulation systems rated for a 65 °C 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 °C 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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| PAR Approval |
2017-09-28
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| PARs |
Additional Resources Details
| Historical Base Standard |
Working Group Details
| Working Group |
InsLife-WGC57.91 - Insulating Life - Loading Guide Working Group
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| Sponsor Committee | |
| Society | |
| IEEE Program Manager | |
| Existing Standards |
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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General recommendations for loading 65 C rise mineral-oil-immersed distribution and power transformers are covered.
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Errors identified in IEEE Std C57.91-1995 are addressed in this corrigendum.
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This guide provides recommendations for loading mineral-oil-immersed transformers and step-voltage regulators with insulation systems rated for a 65 ?C 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 ?C 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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