IEEE /ANSI phasing standards are shown in Figure 4.
For delta-wye or wye-delta transformers, the primary (H) current leads the secondary current (X) by 30องสา.
How the 30บ phase shift is accomplished within the transformer is a mystery to many engineers. Put simply, it is accomplished by how the delta winding is made up within the transformer.
Figures 5 and 6, respectively, show how this is done for a delta-wye and wye-delta transformer wound to meet IEEE/ANSI standards.