Star Delta CT

[Cerkit]

Hi,

Please see the current distribution I am proposing in the attached as I need to verify which relays will be tripping. Is this correct, for a phase to phase fault at F1 I am getting the attached fault current in the CTs.

 

[waross]

For a single phase load applied to a delta transformer bank, all three phase windings will pass equal current.
If the current is based on the available short circuit current of a single transformer in a bank, then the fault current will be twice that current due to contributions from the unfaulted phases.
But, the current in the unfaulted windings will be at 50% PF (one leading and one lagging) and the resultant current will be equal to the current through the faulted winding.
To verify calculate the fault current across the open side of an open delta connection and then put that in parallel with the current through the faulted winding.
All three lines will pass current. The unfaulted line must pass current to pull the phase angles out to the 50% PF.

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

 

[stevenal]

It's unclear to me what I'm looking at. Which coils are magnetically coupled? In any case there are a few current law violations. One node has 1.73 PU entering from each of two ways with none leaving. Another has 1.73+1.73 leaving with only 1.73 entering.