Comment by qlte

That's the usual failure mode of any grid, aggressive load shedding will be used as a last resort to keep the frequency within tolerances.

The renewable aspect is because historically they were installed with "grid following" inverter systems instead of "grid forming" which can maintain frequency even if temporarily islanded in a partition without spinning mass generators to set frequency.

There's nothing intractable about a 100% renewable grid, the technology exists and has already been deployed in new installations.