Basis for performance, interchangeability, safety and selection divided into two sections as follows: (1) Section.A Transformers rated 3750/4687 through 10 000/12 500 kVA, three-phase. (2) Section.B Transformers rated 12 000/16 000/20 000 through 60 000/80 000/100 000 kVA, three-phase.