Three winding step up generator transformer connection

[niallnz]

Hi all

On a hydro power generation project under construction we have two generators connecting to the power system by a single three winding transformer. The step up transformer consists of three single phase units each with two 13.8kV secondary windings. Our expectation is that the overall configuration will be Ynd5d5. However the contractor wants to connect the transformers such that the overall configuration will be Ynd5d11, due to the location of the terminals on the transformer units this configuration will be easier to implement.

But in doing this connection the magnetic flux from each LV winding will be in opposite directions. So with both generators running will this configuration even work?

Cheers Niallnz

 

[prc]

It depends- in case the two LVs are provided radially with respect to HV, no problem, but if they are provided axially split,it may cause some unexpected problems due to leakage flux from each LV not in line. Better contact transformer manufacturer.