Wind farm step up transformer

[cirtcele]

Any one knows why there are tertiary delta winding used in wind farm substations? For harmonic cancellation or kVAr compensation? It seems to me that the PF regulation is done on the LV side of the same transformer which is 25kV or 34.5 kV. Seems to me this is mainly for harmonic cancellation. The HV side of the same transformer is (usually 138 kV) solidly grounded and the LV side is resistor grounded.
Comments are appreciated
Regards

 

[alehman]

A tertiary delta is sometimes used on YY transformers to provide low impedance zero sequence current shunt. It also provides what amounts to a short circuit for 3rd harmonics.

See thread238-130030