Spain’s Blackout and the Miracle of the Modern Power Grid

Last week, more than 50 million people across mainland Spain and Portugal suffered a blackout that lasted more than 10 hours and shuttered stores, halted trains, and dealt more than $1 billion in economic damage. At least eight deaths have been attributed to the power outage.

Almost immediately, some commentators blamed the blackout on the large share of renewables on the Iberian peninsula’s power grid. Are they right? How does the number of big, heavy, spinning objects on the grid affect grid operators’ ability to keep the lights on?

On this week’s episode of Shift Key, Jesse and Rob dive into what may have caused the Iberian blackout — as well as how grid operators manage supply and demand, voltage and frequency, and renewables and thermal resources, and operate the continent-spanning machine that is the power grid. Shift Key is hosted by Robinson Meyer, the founding executive editor of Heatmap, and Jesse Jenkins, a professor of energy systems engineering at Princeton University.

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Here is an excerpt from our conversation:

Robinson Meyer: So a number of people started saying, oh, this was actually caused because there wasn’t enough inertia on the grid — that Spain kind of flew too close to the sun, let’s say, and had too many instantaneous resources that are metered by inverters and not by these large mechanical generators attached to its grid. Some issue happened and it wasn’t able to maintain the frequency of its grid as needed. How likely do you think that is?

Jesse Jenkins: So I don’t think it’s plausible as the precipitating event, the initial thing that started to drive the grid towards collapse. I would say it did contribute once the Iberian grid disconnected from France.

So let me break that down: When Spain and Portugal are connected to the rest of the continental European grid, there’s an enormous amount of inertia in that system because it doesn’t actually matter what’s going on just in Spain. They’re connected to this continen- scale grid, and so as the frequency drops there, it drops a little bit in France, and it drops a little bit in Latvia and all the generators across Europe are contributing to that balance. So there was a surplus of inertia across Europe at the time.

Once the system in Iberia disconnected from France, though, now it’s operating on its own as an actual island, and there it has very little inertia because the system operator only scheduled a couple thousand megawatts of conventional thermal units of gas power plants and nuclear. And so it had a very high penetration on the peninsula of non-inertia-based resources like solar and wind. And so whatever is happening up to that point, once the grid disconnected, it certainly lacked enough inertia to recover at that point from the kind of cascading events. But it doesn’t seem like a lack of inertia contributed to the initial precipitating event.

Something — we don’t know what yet — caused two generators to simultaneously disconnect. And we know that we’ve observed oscillation in the frequency, meaning something happened to disturb the frequency in Spain before all this happened. And we don’t know exactly what that disturbance was.

There could have been a lot of different things. It could have been a sudden surge of wind or solar generation. That’s possible. It could have been something going wrong with the control system that manages the automatic response to changes in frequency — they were measuring the wrong thing, and they started to speed up or slow down, or something went wrong. That happened in the past, in the case of a generator in Florida that turned on and tried to synchronize with the grid and got its controls wrong, and that causes caused oscillations of the frequency that propagated all through the Eastern Interconnection — as far away as North Dakota, which is like 2,000 miles away, you know? So these things happen. Sometimes thermal generators screw up.

Music for Shift Key is by Adam Kromelow.