1.1 This standard is intended to set forth characteristics relating to performance, limited electrical and mechanical interchangeability, and safety of the equipment described, and to assist in the proper selection of such equipment. NOTE — Refer to the latest Federal Regulations concerning polychlorinated biphenyls (PCB) contamination in transformers. 1.2 This standard describes certain electrical and mechanical characteristics and takes into consideration certain safety features of three-phase, 60-Hz, liquid-immersed, self-cooled, underground-type distribution transformers rated 2500 kVA and smaller with high voltages of 34 500GrdY/19 920 volts and below and with low voltages of 480 volts and below. These transformers are generally used for step-down purposes from an underground primary cable supply and are suitable for occasional submerged operation. 1.3 This standard does not cover the electrical and mechanical requirements of any accessory devices that may be supplied with the transformer.