Standard for Overhead Type Distribution Transformers@ 500 kVA and Smaller: High Voltage@ 34500 Volts and Below: Low Voltage@ 7970/13800Y Volts and Below (Replaces NEMA C57.12.20-1997)
This standard is intended for use as a basis for determining the 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- and three-phase@ 60-Hz@ mineral-oil-immersed@ self-cooled@ overhead-type distribution transformers 500 kVA and smaller@ with high voltages 34500 volts and below and low voltages 7970/13800Y volts and below. Such transformers may include one or more of the following features: 1) High-voltage@ overcurrent protection 2) High-voltage@ overvoltage protection 3) Low-voltage@ overcurrent protection 4) Low-voltage@ overvoltage protection NOTE - For polychlorinated-biphenyl (PCB) contamination in transformers@ refer to the latest federal regulations.