You think this is bad
There was a plan fortunately busted, to attack the time references used for synchronizing grids.
Ironically there are only a few of these even with backups, Rb/Cs sources are somewhat immune to jamming but the problem is all you need to do is disrupt a handful of the connections or knock them slowly out of sync in opposite directions (eg 0.2ms/day) and all hell breaks loose in about a week if the drift isn't compensated and also spoofed with GPS MITM hack.
Also relevant: hacking relatively badly protected solar grid tied inverters to force a grid fail using a peak load dropout, in theory every single one going out at the same time in say .CA might be enough.
Think unpredicted eclipse.
(deleted link to timing hack, don't want to get Gitmo'd)