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IEEE STD C57.12.01-1998: STANDARD GENERAL REQUIREMENTS FOR DRY-TYPE DISTRIBUTION AND POWER TRANSFORMERS INCLUDING THOSE WITH SOLID-CAST AND/OR RESIN-ENCAPSULATED WINDINGS

IEEE STD C57.12.01-1998: STANDARD GENERAL REQUIREMENTS FOR DRY-TYPE DISTRIBUTION AND POWER TRANSFORMERS INCLUDING THOSE WITH SOLID-CAST AND/OR RESIN-ENCAPSULATED WINDINGS
IEEE standard C57.12.01-1998 on distribution transformer

Abstract: Electrical, mechanical, and safety requirements of ventilated, nonventilated, and sealed dry-type distribution and power transformers or autotransformers, single and polyphase, with a voltage of 601 V or higher in the highest voltage winding, are described. Information that can be used as a basis for the establishment of performance, interchangeability, and safety requirements of equipment described, and for assistance in the proper selection of such equipment, is given.

Introduction: This standard, together with its companion standards documents, represents a new milestone in standards for dry-type transformers, which are becoming increasingly more important with the elimination of askarel insulating fluids in new transformers. This standard is the result of an effort encompassing the interests of users, manufacturers, and others dedicated to producing voluntary consensus standards primarily for dry-type transformers.

This revision was developed to recognize dry-type transformers with solid-cast and resin-encapsulated windings. The Working Group that developed the revision identiÞed requirements for IEEE Std C57.12.01-1989, incorporating dry-type transformers with solid-cast and resin-encapsulated windings in 3.1 through 5.10, 5.12, and 6.52 of this standard. In addition, new materials and coil design techniques necessitated a revision that recognizes factors that differ from conventional design of dry-type transformers.

Previous editions of this standard used a constant 30 ¡C difference between hottest-spot and average winding temperature rises for a kVA range from 1Ð20 000 kVA. Since the last revision of this standard, a Working Group reviewed hottest-spot and average temperature-rise data. Several manufacturers of different transformer designs conducted extensive test programs.

The Working Group concluded that the difference between the hottest-spot and average temperature rise was dependent on the size and design of the transformer. For some large transformer designs the difference may exceed 30 ¡C, however, for small units, the difference is considerably below 30 ¡C. The Working Group recommended a constant ratio of hottest-spot to average winding temperature rise for the various insulation temperature classes.

This approach improves harmonization with international standards such as IEC 60050-726:1982. The revision of this standard clarifies the requirement that hottest-spot temperature rise is a performance criteria to be met by the manufacturer. Calculation of hottest-spot temperature rise is required by this revision; however, future study is planned to develop test procedures to verify hottest-spot temperature rise.
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  1. SaipowercontolsNovember 5, 2012 at 7:43 PM

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