Well @Ingar a pretty-cheap drone could easily blow up either a transformer or (even less-armored) those nice balancing caps you see in the substation. Those are probably not all that tough to replace but still, until you do you're ****ed and hitting a transformer in the cooling fins will definitely disable it until that can be fixed even if its protection is effective and it doesn't destroy itself by melting or catching fire. Hell, it would be trivial to hit any high-voltage transmission line simply by hitting the insulators on the tower; break free one of those and the cable is going to fail from physical overstress taking that segment out until it can be fixed. Its pretty cheap to do something like that thus someone interested in doing it can almost-certainly break it faster than you can fix it. If you get a phase-to-phase short when it goes down the odds are pretty good you'd do material damage to the gear on at least one end of that line too.

Such an attack is almost-impossible to prevent or interdict if someone wants to do it; there are simply too many places it can be targeted at and there's no possible way to defend them at scale.

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