> Much of the damage to the power grid can mostly be mitigated by turning off electricity
That isn't entirely true.
I guess, in reality, "turning off electricity" can work, if "turning off" means shutting down generation at the same time throughout an entire interconnected grid and physically disconnecting literally every transformer throughout that transmission grid before they're cooked by geomagnetically-induced current (GIC).
Induced DC current alone can heat the windings in high-voltage transformers to the point of catastrophic failure, and that's assuming they can disconnect the AC current already flowing through the windings—if they can't, it heats even faster. This can possibly be mitigated by using a CT or hall sensor combined with a separate winding to cancel out the flux in the transformer's core, but I suspect that kind of work hasn't been done because there's no cost benefit.
Some electricity providers have relaying systems in place meant to protect equipment, but the last time that was tested in real-world conditions (1989, in Québec) they failed to prevent equipment damage.
That says nothing about the transmission lines themselves, most of which are nowhere near protected from GIC, and could either overheat or allow enough DC to flow through smaller pole-mounted transformers , which magnetizes them and dramatically reduces their serviceable life (if not outright destroying them).
In the case of Hydro-Québec, GIC didn't cause equipment damage; their protection systems—the stuff meant to "turn off the electricity"—allowed damage to occur anyway.
That isn't entirely true.
I guess, in reality, "turning off electricity" can work, if "turning off" means shutting down generation at the same time throughout an entire interconnected grid and physically disconnecting literally every transformer throughout that transmission grid before they're cooked by geomagnetically-induced current (GIC).
Induced DC current alone can heat the windings in high-voltage transformers to the point of catastrophic failure, and that's assuming they can disconnect the AC current already flowing through the windings—if they can't, it heats even faster. This can possibly be mitigated by using a CT or hall sensor combined with a separate winding to cancel out the flux in the transformer's core, but I suspect that kind of work hasn't been done because there's no cost benefit.
Some electricity providers have relaying systems in place meant to protect equipment, but the last time that was tested in real-world conditions (1989, in Québec) they failed to prevent equipment damage.
That says nothing about the transmission lines themselves, most of which are nowhere near protected from GIC, and could either overheat or allow enough DC to flow through smaller pole-mounted transformers , which magnetizes them and dramatically reduces their serviceable life (if not outright destroying them).
In the case of Hydro-Québec, GIC didn't cause equipment damage; their protection systems—the stuff meant to "turn off the electricity"—allowed damage to occur anyway.