zero sequence imp for a Delta/Star transformer

[ksenyatsi]

hi, if i want to test the Zeoro sequence impedance of a Delta/Star transformer, how do i do it. am i correct to test it on te Secondary Star connection ith a neutral? pls help.

 

[cranky108]

Why don't you contact delta/star.

 

[alehman]

Perhaps cranky108 is a bit cranky.

1. Connect all three terminals together.
2. Apply a voltage between the shorted terminals and neutral.
3. Measure the current.
4. Divide the former by the latter.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[electricpete]

Just thinking out loud, the zero-sequence impedance for thru-fault on delta-wye transformer would be infinity, wouldn't it?....Or is there some different scenario of interest besides a thru-fault?

=====================================
(2B)+(2B)' ?

 

[alehman]

Looking in to the delta winding would be infinite. On the wye side, you would see Z0 plus 3X any impedance in the N-G lead.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[cranky108]

I would think Delta-star would have records of the testing they did in the past, or at least the designed impedance.

 

[electricpete]

Maybe the op should clarify whether he meant Delta/Star the OEM or Delta/Star the winding configuration. (some use star interchangeably for wye).



=====================================
(2B)+(2B)' ?

 

[electricpete]

btw - thanks Alan for responding. I guess this zero sequence impedance must be of interest for faults other than thru-faults.

=====================================
(2B)+(2B)' ?

 

[dpc]

It is of interest for any ground faults on the wye side of the transformer.

David Castor

http://www.cvoes.com

 

[alehman]

electripete - I took "Delta/Star" to mean the winding configuration. Thanks for clarifying. We need the OP to respond.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[ksenyatsi]

thanks Guys. the Delta/Star i meant the windings configu primary Delta and secondary Star.

 

[waross]

Hi Pete;
A ground fault on one phase of the wye will be seen as a phase to phase fault on the primary. The current for a single phase load will be supplied from all three primary windings.
50% of the current will be supplied by the "in phase" winding.
50% of the current will be supplied by the other two windings, one at a leading phase angle and one at a lagging phase angle.
This is in a perfect world. In the real world the impedances of the supply conductors may skew the percentage slightly.


Bill
--------------------
"Why not the best?"
Jimmy Carter