I am not an expert on long-distance transmission lines, but according to that presentation the failures are not caused by instantaneous overvoltage / arc-over (microseconds), but rather by DC imbalance and overheating (seconds to minutes). Which means a better protection technology can fix it, turning permanent equipment damage into temporary shutdowns.

The latest example is 1989 Quebec power blackout: https://en.wikipedia.org/wiki/March_1989_geomagnetic_storm . The storm tripped some protections, that overloaded other circuits which tripped as well, and the whole province went dark. It took 90 seconds for everything to shut down, and 9 hours to restore everything. Judging by that timeline, no major equipment was damaged.

I keep reading about government mandating solar storm protection for power grids.. hopefully next time a big storm comes, we'll be more protected than Quebec in 1989.