step-up transformer neutral grounding

[oluyomi]

3 nos of 400V generators synchronised and have common outgoing connected to the LV side of a 3500KVA 415V/11KV step-up transformer Dyn11 star 415V side and delta 11KV side. Should the neutral of the LV side of the transformer be connected to earth [grounded]?

 

[Kiribanda]

oluyomi,
For me it is not a wise decision.Since you are generating and seems to be exporting power to Utility at 11 kV,this issue would not have come if you use a YNd11 transformer,where 11 kV side is WYE-Earthed.Did your Utility recommend to use a Dyn11 instead of YNd11? or is it an in-house generation only?

 

[Khalid1970]

Your selection is not OK as I faced this problem before (dY Transformer was the best choice).


Now you should ground the generator neutral only and not the Y side of transformer as this will lead to current circulation of the harmonics generated by the generator due to the pitching.


Second issue is that you have no earth reference on the MV side (delta side) which is a problem and that can be overcome by applying a zigzag transformer