In the short circuit calculation, PGM models the "source" object's internal impedance in per unit, while the IEC 60909 uses the equations in the screen shot below which is in ohm and considers the voltage factor (c) whose value differs according to certain considerations detailed in the norm. Considering minimum short circuit calculations, both PGM modeling and IEC modeling give the approximately the same results giving that the c factor in this case =1. However, in other cases both models would not be similar due to this c factor. Moreover, even in minimum short circuit calculations we are still getting small difference (~+2.5%) between our internal solution and PGM and apparently we are getting a factor 1.1 between the Sk_input and the Sk_calculated in PGM.
In the short circuit calculation, PGM models the "source" object's internal impedance in per unit, while the IEC 60909 uses the equations in the screen shot below which is in ohm and considers the voltage factor (c) whose value differs according to certain considerations detailed in the norm. Considering minimum short circuit calculations, both PGM modeling and IEC modeling give the approximately the same results giving that the c factor in this case =1. However, in other cases both models would not be similar due to this c factor. Moreover, even in minimum short circuit calculations we are still getting small difference (~+2.5%) between our internal solution and PGM and apparently we are getting a factor 1.1 between the Sk_input and the Sk_calculated in PGM.