answered 2018-10-23 08:16:35 -0500
Change the phase shift of the generator step-up transformer with 20 degrees. For example use API:
psspy.two_winding_chng_4(3008,3018,r"""1""",[],[_f,_f,_f,_f,_f, 20.0])
to change for generator at bus 3018 in savnw.sav.