This standard covers certain electrical, dimensional, and mechanical characteristics and takes into consideration certain safety features of 60-Hz, two-winding, liquid-immersed transformers rated as follows, and used for stepdown or step-up purposes:

a) 833/958 through 8333/10 417 kVA, single-phase; 750/862 through 10 000/12 500 kVA, three-phase; high voltage, 2400 through 138 000 volts; low-voltage, 480 through 36 230 volts—without load tap changing;

NOTE—A subgroup of the above group is also identified as three-phase transformers 750-2500 kVA, with distribution BIL characteristics.

b) 12 000/16 000/20 O00 through 60 000/80 000/100 000 kVA, three-phase; high voltage, 23 000 through 230 000 volts; low voltage, 4800 through 36 230 volts—without load tap changing;

c) 3750/4687 through 10 000/12 500 kVA, three-phase; high voltage, 6900 through 138 000; low voltage, 2400 through 36 230 volts—with load tap changing;

d) 12 000/16 000/20 000 through 60 000/80 000/100 000 kVA, three-phase; high voltage, 23 000 through 230 000 volts; low voltage, 4800 through 36 230 volts—with load tap changing.

It is not intended that this standard apply to dry-type, regulating, pad-mounted, secondary-network, furnace, rectifier, or mine transformers.