Wye-Wye? Why would you use this type of transformer? I have just seen a drawing that had a substation with a primary switch and the transformer (1500/1995Kva) at 12470-480Y/277V. The drawings and specifications called for the transformer to be a ?5-leged core? for a Wye-Wye. My question is why not connect the transformer as a delta-wye is there any advantage to a wye-wye? This type will also allow currents to flow to the primary also correct?