The 'Three-Phase Fault' block can be used to model short-circuit behavior in a system. Initially, the fault block remains open and, when triggered, it creates a low-resistance path between the phases and ground.
The parameter 'Ron' represents the impedance of the arc through which the fault current flows. It effectively acts as a low-resistance switch between the phases and ground (or between phases), activated at the specified fault time.
Please refer to the below documentation of 'Three - Phase' for more details:
I hope this helps!
