Spain suffered multiple power incidents in the build up to full blackout

By David Latona, Emma Pinedo, Pietro Lombardi

MADRID (Reuters) -Spain suffered several power glitches and industry officials sounded repeated warnings about the instability of its power grid in the build up to its catastrophic blackout on Monday.

The government has ordered several investigations into the blackout. Industry experts say that whatever the cause, the mass outage and earlier smaller incidents indicate the Spanish power grid faces challenges amid the boom of renewables.

A surplus of energy supply can disrupt power grids in the same way as a deficit, and grid operators must maintain balance.

In the week before the blackout, Spain saw several power surges and cuts. 

A power cut disrupted railway signals and stranded at least 10 high-speed trains near Madrid on April 22. Transport Minister Oscar Puente said excessive voltage in the power network had triggered disconnections to protect substations.

On the same day, Repsol's Cartagena refinery saw its operations disrupted by power supply problems.

The grid suffered from significant instability in the days before the blackout, said Antonio Turiel, a senior researcher with the Spanish National Research Council.

Spain's grid operator REE did not reply to a request for comment. Spain's energy ministry declined to comment. 

Spain has ordered inquiries involving government, security agencies and technical experts. A high court judge has launched a probe into whether a cyber attack was to blame.

The Spanish power grid had been on a knife edge for several days due to power system imbalances, said Carlos Cagigal, an energy expert who advises private firms on renewable and industrial projects.

Prime Minister Pedro Sanchez and power grid operator REE's chief Beatriz Corredor have both said record levels of renewable energy were not to blame for Monday's blackout.

But REE and Europe's power grid lobby ENTSO-E had both previously warned that the rapid rise of power generation from renewables could destabilise the grid.

Small renewable generators were putting extra pressure on the infrastructure, REE said in a 2024 report, and REE's parent company Redeia said in February the grid lacked information from smaller plants to be able to operate in real time.

INCREASING RISK OF POWER CUTS

The risk of power cuts is rising, Redeia warned because the closure of coal, gas-fired and nuclear plants reduces the grid's balancing capacities.

"This could increase the risk of operational incidents that could affect supply and the company's reputation," the company said.

Solar farms generate direct current (DC) power which doesn't have a frequency like alternating current (AC) power generated by conventional plants. DC power needs to be converted to AC in inverters to be transmitted via grids.

If solar generation drops, the grid requires backstop AC power to prevent frequency dropping below dangerous levels after which most power contributors disconnect from the grid.

"Shutting down the nuclear plants may put electricity supply at risk," REE's former chair Jordi Sevilla told Spanish news website Voxpopuli in January. Spain plans to shut down all seven nuclear reactors by 2035.

The planned closure of two nuclear reactors at southwestern Spain's Almaraz plant, starting in 2027, will increase the risks of blackouts, European power lobby ENTSO-E said in April.

REE responded to ENTSO-E by saying there was no risk of a blackout and it could guarantee stable energy supply.

Less than a week later, Almaraz temporarily shut down the two units citing abundant wind energy supply as making operations uneconomic. One unit was still offline on Monday.

The blackout across Spain and Portugal knocked out communications and transport systems, shut down industry and offices and brought commerce to a virtual standstill.

The blackout could have shaved 1.6 billion euros ($1.82 billion), or 0.1%, off GDP, Spain's business lobby estimated.

(Reporting by David Latona, Emma Pinedo, Pietro Lombardi, Andrei Khalip and Sergio Goncalves, additional reporting by Graham Keeley, writing by Aislinn Laing; Editing by Ros Russell and Dmitry Zhdannikov)