It is calculated only the DC side, is taken as the maximum current
that can circulate in the cable. The calculation is different
depending on the connection that performs the cable:
Isc in string cable: It is
the short circuit current of a single PV module (declared by the manufacturer).
Isc in connection from string to
electrical panel: It is equal to the short circuit current of
the single module only if the cable itself is protected by a fuse
incoming to the electrical panel. In the case of cable is not
protected, the short circuit current is the sum of the short circuit
current of all strings in parallel minus one.
Isc in connection from electrical
panel to electrical panel: You are using the same process of
connecting cables between strings and electrical panels.
Isc in connection from electrical
panel to Inverter: Consider the MPP tracker to which the cable
is connected, the short-circuit current on the cable is the sum of
current Isc from the parallel inputs to what is considered.