In my area the sub-station already has those safety features in place, if you tried a attack with a 'bow and arrow, with think wire" it would do anything, other then disrupt the system for a few minutes, before it determines whether there's something wrong like a short, before powering back up. And the company responds quickly to any sub-station issues, to make sure the system reset, or to physically inspect any problems..
About 5 years ago, a snake took out my substation for 5+ days. I think you greatly over-estimate the level of monitoring and response times.
The Cyber FUD is like the Y2K FUD of 15 years ago and the EMP FUD and the Solar Flair FUD... All designed to make you fear something most of us don't understand.
Y2K wasn't FUD. 95% of it was needed work to prevent more expensive failures after. Yes, a broken date on a system clock isn't that bad, unless your accounting software uses the date, and you accidentally send out 99 years of pay for the next pay stub (amazingly enough, back then and even now, there are few systems that have flags thrown up for unusual amounts). It isn't going to kill anyone (like flying an F-22 across the date line, or taking off from below sea level could have), but there would have been mass confusion and unplanned error fixes. It was easier to spend 6 months doing firmware updates, and replacing old hardware, and the software updates needed so things would work. And even after, there were still lots of little issues with dates.
EMP is FUD until North Korea detonates a nuke 500 miles above MO/KY (I'd go MO/KY to lean east to ensure the loss of NYC, but they could go KS and hope to get all of CA and NY), taking out NASDAQ, Wall Street, the power grid, and 99% of all cars in the continental US. That's the worst-case WWIII scenario.
Solar flares have yet to cause anything more than a mild increase in bit errors in ICs.
IF I HAD A MINE SHAFT, I don't think I would just abandon it. There's got to be a better way. -- Jack Handley, The New Mexican, 1988.