At the hazard of making a fool out of myself...
IIRC, by their very design, PV (wave matching) inverters are sync'd to the utility's waveform.
If this fails to be true, they will trip out.
If that is true, then when a bus is backfed grid inter-tied PV power it can't stack up on top of the amps provided by the utility. For the inverter will not be functioning at the exact same voltage -- but a tad higher. Hence, the PV inverter will displace current back up towards the Poco.
Should the load-side go into fault mode, (bolted short) IIRC, the inverter trips open.
So stacking of the amperages sounds over-engineered -- for PV inverter-interties. (only)
Beyond that, there's a general mis-understanding WRT PV current during a bolted short. Unlike an infinite bus (Poco power) PV arrays are semi-conductor devices -- which S A T U R A T E curret flow under a bolted short.
Restated: they are not at all capable of generating the transitory amperages possible with inductive elements. (Transformers, alternators, generators) Unlike PV cells, inductive elements store EM energy -- which has to be absorbed during a bolted short. Hence, fuses and C/Bs.
PV cells have no collapsing field effects at all. The only inductive and capacitive elements would be in the inverter -- and, IIRC, the factory has them internally protected/ fused.
Since I don't work the PV side of the street, I'd appreciate comments from installers that do.
