Article: MVA Short Circuit from ETAP

[JUANPE]

The short circuit apparent power is for the symetrical three-phase fault for your circuit --> S= 1500 MVA . It´s a net parameter, independient of the fault type.
The first expression for the symetrical short citcuit current is OK.
Ik3''=(c*Un)/(sqrt(3)*|z(1)|) or as you noted, according to IEC 60909


For a line to ground fault the expresion is (for symetric components):

Ik1''=(sqrt(3)*c*Un)/|Z(1)+Z(2)+Z(0)| according to IEC 60909, if the fault is far-from generator Z(1)=Z(2), and the Z(0) is function of the earth system.
If you choose a value for Z(0)=200 ohms for overhead lines and Z(0)= 60ohms for an underground network. Normally, the electric company limit the zero sequence current to 300A or 1000A respectively, to avoid dangerous step and touch voltage to people.