IEEE C57.12.21-1992 pdf free.American National Standard Requirements for Pad-Mounted,Compartmental-Type Self-Cooled, Single-Phase Distribution TransformersWith High Voltage Bushings; High-Voltage,34500 GRYD/19920 Volts and Below; Low-Voltage,240/120 Volts; 167 kVA and Smaller. IEEE C57.12.21 This standard is intended for use as a...