They might have lacked the knowledge of "the grid" to make such an attack go beyond one county, but there was some degree of thought put into that attack.
It's easier to attack than defend.
Information about the larger structure of the grid, transmission direction, system redundancies/tolerances, failure cascades is a lot harder to come by. You could build up a picture by accumulating OSINT resources, mapping gaps, making physical observations etc., but synthesizing that into any sort of working model of the grid itself would require some pretty advanced engineering expertise and a lot of institutional knowledge even at the local level. Anyone with sufficient smarts, training, and know-how is a lot more likely to be invested in the integrity of the grid than its sabotage.
Also, in purely economic terms it's not efficient for an antagonist to max out resources on trying to land a decisive masterstroke. It takes a lot of time, money, and moving parts to pull off such an attack. An ongoing rash of cheap micro-attacks, even poorly correlated, drives up costs in ratchet fashion, without any threat being sufficiently expensive to bring about massive change (eg burying major parts of the transmission infrastructure, switching to a different architecture, radically different security posture). The strategic goal is to raise the cost of 'normal' above the market's willingness to bear, and then exploit social/political failure modes.
Shorted winding == complete replacement needed for high voltages, and a single bullet would be more than enought to break insulation on the winding many times.
"If the windings within the transformer itself were damaged, it would probably require replacement of the equipment. Transformers of this scale are rarely manufactured without an order, which means we don’t have a lot of spares sitting around, and the lead time can be months or years to get a new one delivered, let alone installed."
Interestingly, I'd wager that very little infrastructure in developed countries was designed with any thought of defending it from it's own citizens.
The electrical grid is largely ignored because it’s so big and distributed over such a large area it’s difficult for small groups to attack it successfully. So the focus is on limiting cascading failures. Shooting equipment only caused local damage and things got back to normal in a week.
It was unpleasant for those affected, but you can catch people conducting repeated attacks a lot easier than you can harden all this infrastructure.
Russia has been bombing Ukraine infra from Oct, used thousands of missiles and things are still running - https://en.m.wikipedia.org/wiki/2022%E2%80%932023_Russian_st....
running from the radiation released from the shelling of nuke plants, not running in the "performing normally" sense
"Radiation levels increased about 20-fold on Thursday"
https://web.archive.org/web/20220225165134/https://www.bbc.c...
65 microSv or 65 µSv is a really trivial amount. It should inspire a yawn not a yikes.
Seems it was not from the shelling.
We think you're missing the larger point
One fairly simple defense is to set up an opaque wall around it, so if they are outside the perimeter fence they cannot see the target.