Three winding transformers

[Bob357]

In a wye - grounded wye - delta transformer, how does load unbalance on the secondary (the grounded wye winding) reflect into the primary (ungrounded wye winding) and the tertiary (delta) winding? The transformer in question is a 15 MVA, 69 kV - 12.47 kV with a 30% delta 4800 volt tertiary.

 

[DiscoP]

For an unbalanced load, all the current would be reflected back to the primary wye winding. No current will flow in the delta.
You would only get current flow in the delta during a ground fault.