Will a Delta-Delta transformer backfeed into the primary source?

[11bgrunt]

Will a three-phase transformer, wound Delt-Delta, backfeed on a single primary phase loss?
AI says yes. I don't know that I agree, if there is no three-phase load on that transformer.

Sent by Copilot:​

Yes, a three-phase transformer with a Delta-Delta configuration can backfeed if there is a loss of a single primary phase. In a Delta-Delta transformer, each phase is connected in a closed loop, which allows the transformer to continue operating even if one of the primary phases is lost. However, this can lead to unbalanced voltages and currents, which may cause overheating and potential damage to the transformer and connected equipment.

 

[jim dungar]

Yes a backfeed is possible, if there are currents circulating in the core.
This is one reason some utilities do not like common core construction for delta-delta transformers. Most 'electronic' multifunction relays have negative sequence functions to sense the loss of a single primary phase.