Blown up power flow solution right after adding short circuit data at the swing generator

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I am connecting an infinite generator at a bus (swing bus) and then a branch with R and X values obtained from the short circuit data connects this bus to my system. This is to consider the contribution of the utility side during the dynamic simulation. But I am stuck with a blown up power flow before even considering the system dynamics. I haven't been able to narrow down the problem. I am sure the system is set up right as I was able to run the power flow before adding that R and X branch i.e., the infinite generator with no short circuit data.

Any help in this regard would be very helpful and appreciated.