IEEE/ANSI C57.12.51-1981

Superseded.

This new dry-type transformer standard describes ventilated dry-type transformers with self-cooled kilovolt-ampere ratings 501 to 7500 and high voltages 601 to 34 500 volts; forced-air-cooled ratings for certain sizes are listed in Part II. (American National Standards Committee on Specialty Transformers, C89, has responsibility for transformers with high voltages 600 volts and below.)

This standard is part of a new series of dry-type standards that also includes:

• American National Standard General Requirements for Dry-Type Distribution and Power Transformers, ANSI/IEEE C57.12.01-1979;
• American National Standard Test Code for Dry-Type Distribution and Power Transformers, ANSI/IEEE C57.12.91-1979;
• American National Standard Requirements for Ventilated Dry-Type Distribution Transformers, 1 to 500 kVA, Single-Phase, and 15 to 500 kVA, Three-Phase, with High-Voltage 601 to 34 500 Volts, Low-Voltage 120 to 600 Volts, ANSI C57.12.50-1981;
• American National Standard Requirements for Sealed Dry-Type Power Transformers, 501 kVA and Larger, Three-Phase, with High-Voltage 601 to 34 500 Volts, Low-Voltage 208Y/120 to 4160 Volts, ANSI C57.12.52-1981.

This standard is intended to set forth characteristics relating to performance, limited electrical and mechanical interchangeability, and safety of the equipment described, and to assist in the proper selection of such equipment.

This standard describes certain electrical and mechanical characteristics and takes into consideration certain safety features of 60-Hz, two-winding, three-phase, ventilated dry-type transformers with self-cooled ratings 501 kVA and larger, generally used for step-down purposes. Forced-air-cooled ratings for certain sizes are listed in Part II.

Specific rating combinations are described in the range from 750/1000 to 7500/10,000 kVA inclusive, with high voltage 2400 to 34,500 volts inclusive and low-voltage 208Y/120 to 4160 volts inclusive.

This standard does not apply to other types of transformers such as:

• specialty, ventilated dry-type 500 kVA and smaller
• sealed dry-type
• pad-mounted dry-type
• liquid immersed
• instrument
• regulating
• furnace
• mine
• rectifier transformers

Transformers with high voltage 600 volts or less are excluded.

When this standard is used on a mandatory basis, the word "shall" indicates mandatory requirements, and the words "should" and "may" refer to matters that are recommended and permissive, respectively, but not mandatory.