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Document NEMA C57.12.21 is offered by IHS as part of an online subscription. This subscription contains many documents on the same topic.
You may also purchase this document alone from the IHS Standards Store.
NEMA C57.12.21 Document Information:
Title
Pad-Mounted, Compartmental-Type, Self-Cooled, Single-Phase Distribution Transformers with High-Voltage Bushings; High -Voltage, 34 500 GrdY/19 920 Volts and Below; Low-Voltage, 240/120 Volts; 167 KVA and Smaller, Requirements for
National Electrical Manufacturers Association
Publication Date:
Jan 1, 1980
Scope:
This standard is intended for use as a basis for determining performance, interchangeability, and safety of the equipment covered, and to assist in the proper selection of such equipment.
This standard covers certain electrical, dimensional, and mechanical characteristics and takes into consideration certain safety features of single-phase, 60-Hz, mineral-oil-immersed, self-cooled, pad-mounted, compartmental-type distribution transformers with high-voltage bushings. These transformers are rated 167 kVA and smaller with high voltages of 34 500 GrdY/19 920 volts and below for operation between one phase and grounded neutral, and low voltages of 240/120 volts. These transformers are generally used for purposes of stepdown from an underground primary cable supply.
NOTE: Refer to latest federal regulations concerning PCB contamination in transformers.
This standard covers bushing and terminal arrangements for both radial and loop feed systems.
This standard does not cover the electrical and mechanical requirements of any accessory devices that may be supplied with the transformer.
All characteristics, definitions, terminology, and voltage designations and tests, except as otherwise specified herein, shall be in accordance with the American National Standards listed in Section 2.
This standard generally conforms with ANSI C57.12.20-1974 and C57.12.20a-1978.
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