IEEE C57.12.26

Description / Abstract: This standard covers certain electrical, dimensional, and mechanical characteristics and takes into consideration certain safety features of three-phase, 60 Hz, mineral-oil-immersed, self-cooled, pad-mounted, compartmental-type distribution transformers with separable insulated high-voltage connectors. These transformers are rated 2500 kVA and smaller, with high voltages of 34 500 Grd Y/19 920 V and below and with low voltages of 480 V and below. These transformers are used generally for step-down purposes from an underground primary cable supply.

NOTE - Refer to latest Federal regulations concerning polychlorinated biphenyl (PCB) contamination in transformers.

This standard covers connector and terminal arrangements for both radial-feed and loop-feed systems. Either certain minimum dimensions (see Figs 1-4) or certain specific dimensions (see Figs 5.A-8) shall be specified.

This standard does not cover the electrical and mechanical requirements of any accessory devices that may be supplied with the transformer.