Abstract: A transformer cooling duct arrangement wherein the transformer winding sections are encompassed by an inner and outer insulating oil barrier and inner and outer blocks are employed to direct the oil flow in a labyrinth path throughout the winding sections. The inner oil block consists of a plurality of individual slotted blocks slidably mounted between corresponding pairs of radial spacers. The slidably mounted block arrangement allows the individual blocks to tightly contact the inner barrier during the transformer dry treatment process.

Abstract: A disc wound winding formed of a plurality of spirally wound, disc coil sections and having series capacitance increasing electrostatic shields in less than all of said sections, incorporates partial-turn electrostatic shields in disc coil sections adjacent that portion of said winding not having electrostatic shields. With this arrangement, a substantial reduction in the change in series capacitance between the shielded and unshielded portions of a disc wound winding is effected which minimizes unsatisfactory impulse voltage build-up at the beginning of the unshielded portion of said winding.