Historical
IEEE Std C57.12.21-1992
American National Standard Requirements for Pad-Mounted, Compartmental-Type Self-Cooled, Single-Phase Distributuon Transformers With High Voltage Bushings; High-voltage, 34500 GRYD/19920 Volts and Below; Low-Voltage, 240/120 volts; 167 kVA and Smaller
Institute of Electrical and Electronics Engineers [ieee]