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> it’s hard to know whether it’s possible to “cold start” the grid at all, much less timely. This is called "black start", and it's something all grid operators plan for and regularly test. How it works is very simple: some power plants are able to start up without the grid (they have their own emergency diesel generators, which in turn have batteries for their own start up), and these power plants can run for a while without any external load. Then it's a careful dance of powering up some high voltage circuits and substations, putting some load on them, powering up more power plants and circuits and substations, putting more load on them, and so on, until all the loads and most of the power plants are connected. It's not a fast process, but it's also not that slow; from those I've read about or experienced, it tends to take less than a day for most of the grid to be back online (and the places which don't come back online are usually due to some local defect). > [...] you’d need to disconnect them all at once (coordinating that between independent operators, and as I understand it isolating these giant grid-scale transformers isn’t just a question of flipping a switch). Then you need to ramp down power production in a balanced way as you ramp down places for it to go [...] It's the opposite. Powering down can be very fast, by design: whenever there's a fault, or parameters like voltage or frequency or power go too far out of nominal, protective devices react by disconnecting whatever they're protecting, so everything on the power grid has to be designed to tolerate being instantly cut off. The worst that happens is that, without anywhere for the power to go, the protective devices on the generators quickly power them down too, and some kinds of generators are very slow to power back up (it can take a whole day for some thermal power plants). |
Tolerate is often key. It can still be better to do gradual shutdown even if you can do the instant one.