Unbalanced fault (slg) in dynamic simulation

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I use it and i am getting the results i describe in the question. Is it data problem or something else happens? I check the results from the angle plotting. When i enter 0 reactance and resistance it always synchronises after the fault. If enter an non-0 value after the fault it desynchronises

OK, so you are talking about the impedance of the SLG fault. (0,0) is solid fault. Whenever non-zero values are used a fault impedance is used and the short circuit is less severe. It is strange that the system becomes less stable. What happens when it desynchronise? One generator out of step?

The relative to the swing bus angle of the generator oscilates!! I find it quite odd because of that reason and i was wondering why that happens. The same thing happened in the savnw i got from jcondos drive. Is there a chance for my PSSE to malfunctioning? Or is it another problem?

I don't understand what you mean. Of course there are oscillations in the rotor angles when you apply a short circuit.

What i mean is when i apply an slg in dynamic sim the system after the oscillations always synchronises, but when i add zf even when i run the fault for 1 cycle it always desynchronises. Do you want me to give you the file to check the slg?