Yes because they have to bring it all back up in phases so that they only face the load spike* from one interconnect at a time, which can take some time and can fail if there’s unknown damage like the GP said.

It really depends on the region though because almost all large hydroelectric dams are designed to be primary black-start sources to restore interconnects and get other power plants back up quickly in phase with the dam. i.e. in the US 40% of the country has them so it’s relatively easy to do. The hardest part is usually the messy human coordination bit because none of this stuff is automated (or possible even automatable).

* the load spike from everyone’s motors and compressors booting up at the same time

Presumably emergency phone comms still work(?) so they could issue instructions to do a phased (heh!) restart to avoid every fridge/air conditioner/whatever restarting at once. Not sure how successful that would be however.

There’s usually two parallel processes going on during a black-start: spinning the power plants back up to get them synchronized to the grid, and getting power back out to all the consumers. Power plants have breakers that disconnect them from consumers which they keep disconnected until independent connections to other power plants allow them to spin up their massive turbines and synchronize them to the grid. There’s also tons of other downstream breakers at substations which will be in various states of functionality.

The power plants with direct connections have hard lines and black-start procedures that get power out to the most important customers like telecom infrastructure, which provides the rest of the comms. In a real world full restart it’s going to mean organizing workers at many substations to babysit old infrastructure so cellular is pretty much mandatory.

And to add more fun, this time they're not dealing with a small number of individual power plants that can be connected with only some phone-call based coordination.

Instead, there are literally hundreds of smaller wind/solar installations. Some of which depend on rapidly fading cellular communication to restart. And some might need an actual site visit to throw on the physical breakers.

Spain is but Portugal is only connected to Spain and they are currently doing a full black start.

For Spain the external power and synchronization can come from France rather than generators which will help, but the process and complexities are still mostly the same. Call it a dark start, perhaps.

Even then, the interconnect capacity with France is currently 2800 MW (was 1400 MW in 2015) with just 3 links, all on the NE.

If Portugal (on the West) had to wait for that, it would probably have taken even longer.

But even a "small" amount of input power makes the process much easier because it can be used to bring up the next source of power.

Sure. Portugal is in deed completely “isolated” if it loses Spain, so it needs black start capability if it wants some degree of autonomy.

As far as containing the issue, this was a disaster. On the flip side, this was as good an opportunity to test a black start as any, it went reasonably well, and the network operator was already in the process of contracting two further dams for the ability.

Presumably not

> A black start is the process of restoring an electric power station, a part of an electric grid or an industrial plant, to operation without relying on the external electric power transmission network to recover from a total or partial shutdown.[1]

https://en.wikipedia.org/wiki/Black_start

The key part of the phrase is actually "electric power station, a part of an electric grid or an industrial plant." Note how the definition doesn't include an entire grid.

Only the first power plant in a black-start (like a hydroelectric dam or gas plant started by a backup generator) is truly "black started." The rest don't fit that definition because they depend on an external power source to spin up and synchronize frequency before burning fuel and supplying any energy to the grid. If they didn't, the second they'd turn on they'd experience catastrophic unscheduled disassembly of the (very big) turbines.

Only the first power plant can come online without the external transmission network.

That’s not necessarily 100 true, as you could have multiple plants black start and then synchronize later.

In fact, if you’re not sure which will start first, you might go that way. They’re all disconnected from the grid at that time anyway.

You’re absolutely right, there are a lot of variations. In this case I think Portugal started from their own hydroelectric dam and restarted everything North to South while Spain started several in parallel from the interconnects to the rest of Europe (can’t tell which interconnect it was though).

Yup - a true black start would be substantially more difficult and time consuming. More like a gradual reconnect.

Then again they might be less prepared precise because of the euro grid is available

It's a complex enough issue that you can't really 'hand wavey' it. The details are specific and thorny.

But not a black start.