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. This standard describes certain electrical and mechanical characteristics and takes into consideration certain safety features of three phase@ 60-Hz@ liquid-immersed@ self-cooled@ undergroundtype 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 stepdown purposes from an underground primary cable supply and are suitable for occasional submerged operation.?