“The exercise was held from May 8 to 9, 2024, at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, and at a Federal Emergency Management Agency (FEMA) site in Denver, Colorado.”
Article refers to a PDF of the report it’s based on:
https://www.jhuapl.edu/sites/default/files/2025-04/Space-Weather-TTX-Report-Summary-v3-FINAL.pdf
At that point, that grid connection will be the least of anyone’s worries. The storm in Quebec in… 1990? Ish. tripped breakers, and shut things down for like a day.
A storm on the scale youre talking about I am pretty sure would wipe out satellites (maybe even take them down due to atmospheric drag?), impact cables other than power like copper laid for internet and phone, etc. Grid-connected power or not you’d be severely impacted and potentially at risk.
Along with tripping breakers, induced currents can also fry some of the massive capacitors that are attached to high-voltage transmission lines. Those are expensive and not quick to replace.
Oh yeah, a large enough solar mass ejection in such a direction that it would directly hit planet Earth would be extremely bad.