jbond
Electrical
- Apr 13, 2005
- 44
Is it true that a fault on the Y side of a DY Tx will translate upstream on the D side by the appropriate turns ratio for a 3Ph fault - however for a line to line or a single phase fault then the current seen upstream is as you would assume by multiplying of the transformer turns ratio and DIVIDED BY SQRT(3)?
I suspect this is because delta winding will balance out the current as seen by the upstream system - the same way that you translate between 3ph current and 1ph current?
Does this also mean that the current seen upstream will not just be the fault current divided by SQRT(3) but will also include the pre-fault load current? (ie the load on the 2 or 1 healthy phases on the star winding of the system will still be drawing their corresponding load without influence of the fault)
This may sound a bit complicated, I hope that you can understand what I'm saying!

I suspect this is because delta winding will balance out the current as seen by the upstream system - the same way that you translate between 3ph current and 1ph current?
Does this also mean that the current seen upstream will not just be the fault current divided by SQRT(3) but will also include the pre-fault load current? (ie the load on the 2 or 1 healthy phases on the star winding of the system will still be drawing their corresponding load without influence of the fault)
This may sound a bit complicated, I hope that you can understand what I'm saying!