Alternate Low-Frequency Dielectric Tests of Delta Transformer Windings

Current test procedures unduly overstress the midpoint of delta transformer windings during low- frequency dielectric testing. A revision to the USAS Transformer Standards (1) has been proposed to allow alternate test procedures to correct this problem and to allow possible economies in the design and testing of such delta winding transformers. This paper has been requested by the IEEE Working Group to explain the proposed revisions.