how to calculate the fault current on D/Yd Tx D side, if Y side has ground fault? 2

[davidy51]

if there is a 20Mva, 35kV/4.16kV, 5%z Tx with D/Yd winding configuration.
if 4.16kV side has single A phase ground fault, theoretically how much is the 35kV side current? on which phase?

 

[mparenteau]

Draw the network and use symmetrical components.

Mike

 

[dpc]

All of the fault current will be in one winding on both sides of the transformer. If you know the Y side current, you can just use the turns ratio between the windings to calculate the current in the one delta winding. Remember to use the line to neutral voltage when determining the turns ratio. Current will be in whatever delta winding corresponds to the secondary A-phase winding. So you'll have current in two phases on the primary side.