Answer Posted / paul

By having multiply vector groups, you have the ability to parallel 2 or more transformers with with different vector groups by altering their connections.

EG. you can change a Yd11 into a Yd1 by changing the HV and LV phase sequence from positive to negative.

So with that in mind a Yd1 can be converted to a Yd5 if required by placing L1 onto L2, L2 onto L3 and L3 onto L1. The reason for the 4 vector group shift is down the fact that you have rotated each phase by 120 degrees

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