Transformer Connections
Transformer Connections
(OP)
We are looking to add a new power transformer to municipal electric system. Currently, they have two (2) delta-to-delta transformers (with load tap changers), each with it's respective zig-zag grounding transformers to provide the ground on the wye distribution system. Upon talking with some transformer manufacturers, they suggested making the third transformer a ungrounded y-to-y ground connection, which would maintain the 0 degrees phase shift and would be more economical. I believe this would work, but I am cautious and still doing research to make sure this would work. Does anyone have a reason why this third transformer connected ungrounded y-to-y ground would not work with the existing delta-to-delta transformers (with separate grounding zig-zags)?
Thank you for any input to the topic.
Thank you for any input to the topic.






RE: Transformer Connections
RE: Transformer Connections
RE: Transformer Connections
A delta/zig-zag configuration will also yield zero phase shift, and may serve as an operational backup to the existing grounding autotransformer(s).
Standalone operation on a contingency basis may preserve lowside zero-sequence characteristics and triplen-harmonic reduction.
Similar to what jghrist has pointed out for the Yy case, ungraded lo-side winding insulation would permit upgrounded operation, but may not be a necessary feature.
RE: Transformer Connections
RE: Transformer Connections
If yes, you are better off keeing the identical arragement for the sake of consistency.
If not, it does not make a difference if you use the identical configuration or not or whether there is a phase shift.
Obvioulsy someone had added, and rightly so, grounding to an originally ungroudned system. If not paralleling, I would rather go with a delta primary and grounded Y secondary transformer, which is a much simpler, safer and reliable system at the same cost as an ungrounded system.