The unprecedented blackout across the Iberian peninsula was primarily caused by REE’s failure to manage a surge in voltage, the Spanish government has said.
On 28 April, a major incident saw millions of households and businesses across Spain, Portugal and southern France suffer the largest power cut in Europe’s recent history.
The source of the outage was traced to a sudden loss of 2.2GW of electricity at Granada substation in southern Spain.
Following an investigation by the government, an official report has now been published detailing that the blackout was due to voltage control.
It points to a series of technical and operational failures that increased the severity of the event. Following the abrupt loss of power generation in Granada, a complicated chain reaction of grid disconnections soon ensued.
Within seconds, similar disconnections had occurred in Badajoz and Seville, and within 30 seconds the entire Iberian peninsula was experiencing a complete blackout.
Sara Aagesen, Spain’s minister of ecological transition and demographic challenge, said that the cause of the blackout was “poor planning” by REE and “improper” actions by the electricity companies.
She said that the failure to calculate the correct mix of energy to allow the grid to absorb a surge in voltage ultimately brought down the entire system.
She said that the nine power plants did not operate as planned as a result of the surge, and so failed to maintain an appropriate voltage level in the power system.
Aagesen said: ”Each and every one of them experienced some degree of noncompliance” and did not “absorb all the reactive power that was expected”.
She added: ”The system did not have sufficient voltage control capabilities. Either because they were not sufficiently programmed, or because those that were programmed did not adequately provide what was required by the standard, or a combination of both.”
The government report also found that REE failed to switch on thermal power stations, which would have helped stabilise the system.
Aagesen said REE “made their calculations and estimated that [switching on more thermal plants] was not necessary at this time. They only set it for the early hours of the day, not the central hours.”
She also made it clear that the cause was not a lack of installed capacity. “There was enough generation capacity to respond” but rather the cause was a “mismanagement” of available energy resources.
According to Reuters, utilities lobby group Aelec, which represents Spain’s main electricity companies including Iberdrola and Endesa, said it agreed that voltage control was the main cause of the outage, and that the responsibility for ensuring that control lay with REE as system operator.
It stated that despite REE having sufficient resources to guarantee voltage control, it “opted to manage voltage with limited synchronous capacity and an unbalanced geographical distribution, which left the system in a vulnerable situation”.
The Spanish government said it would propose measures to strengthen the grid and improve its ability to control voltage in the system.
It would also push to further integrate the Iberian peninsula with the European grid.
Previous studies have shown that that countries on European islands and peninsulas – such as the UK – have more ‘vulnerable’ grids as they must provide their own flexibility and resilience and cannot be propped up as much by neighbouring countries.