scope:

This guide covers general recommendations for loading mineral-oil-immersed power trans-formers, manufactured in accordance with ANSI C57.12.10-1976 [1]¹ and ANSI C57.12.30-1977 [2] and other oil-insulated power transformers up to and including 100 MVA maximum nameplate rating. It is based mostly on aging of the winding insulation. Loading of transformers larger than 100 MVA may be limited by factors other than insulation aging such as stray flux etc. When it is known that such limitations do not exist and insulation aging rather than oil temperature, gassing, tank heating. etc is the controlling factor, this guide may be used. This guide may also be used for askarel filled transformers.

Recommendations for transformers with an insulation system which conforms to the 65 °C , those rated at an average winding temperature rise of 65 °C and a hottestepot temperature rise of 80 °C, are contained in Section 4 of this guide. Recom¬mendations for transformers with an insulation system which conforms to the 55 °C , those rated at an average winding temperature rise of 55 °C and a hottestspot temperature rise of 65 °C, are contained in Section 5 of this guide.

The method used for computer calculation of the Capability Tables for Normal and Moderate Sacrifice of Life in Section 4 and Section 5 of this guide and examples for developing them by hand calculations are contained in Section 6 and Section 7

¹The numbers in brackets correspond to the refer¬ences listed in Section 2 of this guide.