scope:

Foreward 

ANSI C57.12.10-1988, American National Standard for Transformers-230 kV and Below 833/958 through 8333/10417 kVA Single-Phase, and 750/862 through 60 000/80 000/100 000 kVA, Three-Phase without Load Tap Changing; and 3750/4687 through 60 000/80 000/100 000 kVA with Load Tap Changing-Safety Requirements was last issued in 1988. The focus of this revision was to consolidate requirements for single-phase, three-phase, and load tap changing substation transformers into a single document. This update combines C57.12.10-1977 and C57.12.30-1977.

In the fall of 1996, a working group was formed to determine if there was a need to revise this standard or if it was appropriate to reaffirm as written. The need to revise was apparent in order to update specific technologies, correct errors, and revise the document format.

To comply with current standard format styles, segmentation of the standard into Parts A and B was eliminated. This format was originally used to separate "Basic Standard" and "Other" ratings and Construction Features. All references and related standards were also brought up to date. A number of typographical errors were corrected along with specific section references.

Some of the most comprehensive changes were associated with the load tap changing control technology. Clause 6.5.2, Devices and Accessories was significantly expanded and renamed Requirements for Automatic Control. Clause 6.6.5 was also expanded to better define dielectric test requirements. The simplified reference schematic (Figure 7) for paralleling transformers was revised to comply with C37.2 and IEEE Standard 315. The cooling class designation references were changed from two to four characters.

This standard is a voluntary consensus standard. Its use may become mandatory only when required by a duly constituted legal authority, or when specified in a contractual relationship. To meet specialized needs and to allow innovation, specific changes are permissible when mutually determined by the user and the producer, provided that such changes do not violate existing laws, and are considered technically adequate for the function intended.

When this standard is used on a mandatory basis, the words shall and must indicate mandatory requirements; the words should or may refer to matters that are recommended or permissive, but not mandatory.

Suggestions for improvement gained in the use of this standard will be welcome. They should be sent to the American Standards Institute, 1430 Broadway, New York, NY 10018.

Scope

This standard covers certain electrical, dimensional, and mechanical characteristics and takes into consideration certain safety features of 60-Hz, two-winding, liquid-immersed transformers rated as follows, and used for step-down or step-up purposes:

a) 833/958 through 8333/10 417 kVA, single-phase; 750/862 through 10 000/12 500 kVA, threephase; high voltage, 2400 through 138 000 volts; low-voltage, 480 through 36 230 volts-without load tap changing;

NOTE-A subgroup of the above group is also identified as three-phase transformers 750-2500 kVA, with distribution BIL characteristics.

b) 12 000/16 000/20 000 through 60 000/80 000/100 000 kVA, three-phase; high voltage, 23 000 through 230 000 volts; low voltage, 4800 through 36 230 volts-without load tap changing;

c) 3750/4687 through 10 000/12 500 kVA, three-phase; high voltage, 6900 through 138 000; low voltage, 2400 through 36 230 volts-with load tap changing;

d) 12 000/16 000/20 000 through 60 000/80 000/100 000 kVA, three-phase; high voltage, 23 000 through 230 000 volts; low voltage, 4800 through 36 230 volts-with load tap changing.

It is not intended that this standard apply to dry-type, regulating, pad-mounted, secondary-network, furnace, rectifier, or mine transformers.