Paralleling of two or more transformers with different vector group is possible if you apply correct bus termination in primary and/or secondary sides. For example you can to see various bus termination for different vector group and similar transformer connections at paralleling position (e.g Dy… , Yd… , Yy…) in figure below.
On the other hand regarding your concern connection we can write:
Dy5 = Yd7
Dy7 = Yd5
Therefore you can use end figure for paralleling two mentioned transformers.
Caution: Before any interconnection operation you must check the difference phase angles.
Author : Hamid - From: Iran
