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IEEE C57.12.20-2023
IEEE Standard for Overhead-Type Distribution Transformers 500 kVA and Smaller; High Voltage, 34 500 V and Below; Low Voltage, 7970/13 800Y V and Below
Revision Standard - Active. Certain electrical, dimensional, and mechanical characteristics and safety features of single- and three-phase, 60-Hz, liquid-immersed, self-cooled, overhead-type distribution transformers 500 kVA and smaller, high voltages 34 500 V and below, and low voltages 7970/13 800Y V and below are covered in this standard.
Institute of Electrical and Electronics Engineers [ieee]