scope:

Transformers Covered

This recommended practice covers general recommendations for the application, installation, operation and maintenance of single and polyphase dry-type general purpose, distribution, power, and auto-transformers of the following types:

1) Ventilated, indoor and outdoor, self-cooled cooled or forced air cooled

2) Nonventilated, indoor and outdoor, self-cooled or forced air cooled

3) Sealed, indoor and outdoor, self-cooled

Transformers Not Covered

This recommended practice does not apply to the following:

1) Instrument transformers

2) Step voltage and induction voltage regulators

3) Arc furnace transformers

4) Rectifier transformers

5) Specialty transformers

NOTE - Both ventilated and nonventilated transformers may be furnished with windings utilizing materials such as solid insulating material which allow or require different practices from those required in this recommended practice. In such equipment the recommendations in this recommended practice may be modified by specific manufacturer's recommendations.

Purpose

This recommended practice is intended for general use in the application, installation, operation, and maintenance of dry-type transformers manufactured in accordance with ANSI/IEEE C57.12.01-1979 [10]¹, ANSI C57.12.50-1980 [2], ANSI C57.12.51-1981 [3], ANSI C57.12.52-1981 [4] and ANSI/NEMA ST 20-1972 [13]. Familiarity with other American National Standards applying to dry-type transformers and to their protection is assumed and the provisions of those standards are indicated herein only for clarity.

¹The numbers in brackets correspond to the references listed in Section 2 of this standard.