Solar plant - transformer configuration 1

[bozzah]

The site is 8MW and it consists of 4 clusters (each cluster is 2MW package (2MW transformer and 4-500kW inverters)).

Transformer secondary side is 480V (inverter input) and primary is 44kV. I am trying to see a benefit of transformer configuration (pri:Wye-grounded/sec:Wye). The other option is delta/wye-grounded. As inverters generate about 5% or less of THD, I understand that both options will not let through zero sequence (triplet harmonic) back into the system. I am trying obtain more technical explanation for wye-grounded/wye transformer configuration.

 

[ScottyUK]

A good starting point in answering your question would be this old and highly informative publication from GE: GET-3388B

You can assume that a Y/Y transformer will let the triplen components of the 5% THD through, but if that value is current THD and not voltage THD then it is unlikely to be of great concern to the utility.


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