Wouldn’t the grid just come back online momentarily after some sort of disruption? What’s the actual mechanism that disrupts the flow of electricity?
An EMP (and for that matter a CME as well) contains energy that overloads and as a result damages various solid-state components, and some types of vacuum tubes.You can think of an EMP (or CME) as an alternative and unregulated power source, if that helps. Some types of vacuum tubes can be configured to withstand the effects of an EMP (or CME), that’s actually why many vacuum tubes are still in production and are being advanced further, but they’re primarily used in nuclear armament systems and satellites, and there are limits to how much energy they can withstand from an EMP (or CME).
The problem is that it blows out components of the grid.
An EMP induces really large voltages on anything that looks like a large antenna…like a powerline. If you run 1000V through a component that’s only good for 120V you’ll overload it…components will overheat and burnout. Transformers may explode (the filling boils into gas). When the EMP passes that stuff stays burned out.