Through Fault Current

[speedtronic]

I want to understand the concept for through faults in case of transformers.
For example, there is an external fault on secondary side of a generator step up transformer, so when it is said that all through current will pass through the transformer, does it mean that current is now flowing in opposite direction i.e. from the system in to the transformer & generator? If yes then what could be its effect on transformer or generator? Please explain

 

[bomjac]

Depends on the context you mean. From your question it sounds as if you are thinking of a Generator, feeding to a distribution network through the step up transformer with a fault occurring on the transformer secondary..

Any fault on the secondary side of the transformer will provide a fault current from the generator and also a fault path from the distribution network. The generator current will be limited by the impedance of the transformer. Any fault on the HV side with a distribution network connected is likely to catastrophicaly destructive to equipment before the HV networks protection kicks in.

There should be no flow of fault current from the system to the generator, since it would take the easiest path available to it, which in this case would be the fault on the transformer secondary.

A simple single line diagram to better explain your question would help.