Spain Reveals Details of Chain Reaction That Caused Outage

Spain’s most-detailed account yet of the missteps leading to April’s nationwide blackout failed to fully explain why the power grid was so unstable in the first place.

Over 182 pages, including redactions that blot out the names of companies and power stations, the government laid blame at the grid operator for failing to ensure enough backup generation, and on unnamed plant operators for not fulfilling their commitments for the day.

Still, the document falls short of explaining what originally caused voltage surges that the system was unable to cope with, and what could be done, if anything, to prevent that in the future.

The government has kept tight control over the flow of information on what exactly happened on April 28, when more than 50 million people were left without electricity for several hours in the Iberian Peninsula. The situation has become a blame game between power companies, the grid operator and the government. An independent report by European grid group Entso-e is still months away from being published.

The long-awaited report released late on Tuesday focuses on what went wrong in terms of grid management to prevent a voltage stability issue from turning into a catastrophic outage. The document suggests that Spain’s heavy reliance on renewable sources such as solar wasn’t a problem, but the way power supply was handled.

The report recommends various changes to how voltage is managed. That would include new equipment, such as synchronous condensers, which help the grid maintain stability even when there are few traditional power stations in operation.

What Went Wrong?

In the days following the blackout, grid operator Red Electrica offered a summary of what happened in the seconds preceding the blackout, which occurred around half past noon. But small fluctuations on Spain’s grid started much earlier that morning.

Red Electrica took various measures to deal with the issues, such as limiting flows of power through the interconnector with France and connecting additional equipment to the grid to help maintain voltage.

There’s little indication in the report, however, about what caused the swings in voltage and frequency, although more than a paragraph of information is redacted.

Just after noon, the situation got worse after stronger frequency swings hit the grid and caused intense shifts in voltage in the south and west of the country, where three plants would eventually trip just before the blackout, around 12:30 p.m.

During that critical half hour, the grid operator realized that the network had become more vulnerable to the oscillations and less equipped to handle them. Among further measures to stabilize the network, Red Electrica requested a reduction of flows to Portugal and called for more thermal power plants to turn on and be ready to help control the grid’s voltage.

Portugal’s grid operator only agreed for the flow reduction to start 12:45 p.m. at the earliest. Meanwhile, the quickest timeline offered by a thermal power plant to warm up was about 90 minutes, and it only began doing that minutes before the grid collapsed. So neither measure ever came to be implemented in time to help avoid the debacle.

The scramble to stabilize the grid exposes one of the key issues that day. The grid operator had less capacity to control voltage than it had in the previous months. The system had just 11 generation units available as backup, the lowest number this year.

In addition to not having enough buffer that day, the report found that the backup Spain did have didn’t perform properly. Such plants can help the grid operator to manage voltage, with what’s known as reactive power. Essentially the plant operates like a battery, absorbing or providing power and so balancing out the voltage.

But the report found that nearly all the plants didn’t perform as expected that morning. And in the south in particular, where the major power disconnections that led to the blackout began, plants functioned in a way that was inadequate to control the grid’s voltage.

The report adds fodder to the finger-wagging between utilities and the grid operator, which has heated up in recent weeks.

AELEC, an industry group representing utilities such as Iberdrola SA and Endesa SA, said it has “evidence” that its members’ complied with regulatory requirements and that the grid operator had sufficient resources available to ensure voltage control, including synchronous power plants, which it nevertheless decided not to dispatch.

“It chose to manage voltage with limited synchronous capacity and an unbalanced geographical distribution, which left the system in a vulnerable situation,” AELEC said in a statement.

The system operator performed the appropriate calculations and made the relevant decisions in the programming of technical constraints, always assuming that all units would comply with the technical requirements established by regulations, Red Electrica said of itself in a statement. It denied any culpability or mistakes, adding that the utilities didn’t “absorb the reactive power” they were required to.

Photograph: Pedestrians try to use their mobile phones on an unlit street during a power outage in Molins de Rei. Photo credit: Angel Garcia/Bloomberg

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