Eng. Pro Final Exam Problem 12

[no_concentrate]

Eng. Pro Final Exam Problem 12 :
As per my knowledge primary is connected in Delta and secondary is connected in Star. During single line to ground fault on one phase of star connection other two phase i.e b and c will be zero. Since primary and secondary is linked so there will be no flow of current in C (primary ) also. I am confused about for why current will be zero in a phase of secondary.

 

[mnsee]

Since this is a delta-wye xfmr, so phase A on the secondary side is paired with AB on the primary delta- hence current will be on both A and B on the primary side. A phase of the secondary doesn't have a source of current downstream.