Zero Sequence current at YNd transformer 2

[fouadf]

Hi All,

I have a question regarding transformer short circuit current analysis. I want to calculate the current through inside YNd Transformer during 1phase to ground short circuit at the LV side (Delta) of the transformer. My question : is there any zero sequence current through inside the transformer during this case?

Thanks,

Fu

 

[davidbeach]

If the transformer is connected radially, source on the wye side and phase-ground fault on the delta side there is no fault current. That is, there is no fault current unless you can account for the affects of parasitic capacitances. No current in the sequence domain, no current in the phase domain.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[fouadf]

Thanks for the answer sir. How about non radially connected? It is mean there is a SC source both from LV&HV system. In this case is there Zero sequence current inside Tranformer? Thanks

 

[che12345]

Dear Mr. fouadf (Electrical)(OP)28 Oct 22 04:08
"....I have a question regarding transformer short circuit current analysis. I want to calculate the current through inside YNd Transformer during 1phase to ground short circuit at the LV side (Delta) of the transformer. My question : is there any zero sequence current through inside the transformer during this case?..."
The transformer is YNd i.e. primary is in Y with the Neutral (assumed) earthed. The secondary is d i.e. in delta. When the (secondary delta winding) is [earthed only at one point], nothing happens. There is NO zero sequence current through inside the transformer.
Che Kuan Yau (Singapore)

 

[fouadf]

Thanks Mr Che. Agree with you

 

[jghrist]

If there is another source on the secondary side with a zero-sequence path, like a grounded wye generator, there will positive- and negative-sequence current in the transformer, but no zero-sequence current. See attached sequence diagram.

 

[fouadf]

Thanks jghrist