You don't even need to blame a power outage on a solar event. Transmission lines have been privatized and when I researched it 20 years ago no one entity is responsible for actually inspecting the lines end to end. Companies manage their own stuff and no one inspects the lines end to end so it ends up being a confederation of power distribution monitored by NERC who doesn't have any teeth to punish anyone for anything. Literally, to cause a cascade failure just need one region to have a deep enough mismatch between demand and electric production. The region with the "suck" will then pull from other regions they are connected to. If the interconnected regions can't disconnect then that suck will pull down region after region like dominos falling down.
You don't even need to blame a power outage on a solar event. Transmission lines have been privatized and when I researched it 20 years ago no one entity is responsible for actually inspecting the lines end to end. Companies manage their own stuff and no one inspects the lines end to end so it ends up being a confederation of power distribution monitored by NERC who doesn't have any teeth to punish anyone for anything. Literally, to cause a cascade failure just need one region to have a deep enough mismatch between demand and electric production. The region with the "suck" will then pull from other regions they are connected to. If the interconnected regions can't disconnect then that suck will pull down region after region like dominos falling down.