Power Grid Failures Are Complicated: Lessons from the Iberian Peninsula Blackout

The blackout took place on April 28th 2025 when a large portion of the peninsula’s power delivery system went offline for 10-plus hours.
Aug. 19, 2025
4 min read

Have you been following the Iberian Peninsula blackout that impacted the power grid in Spain and Portugal? The blackout took place on April 28th 2025 when a large portion of the peninsula’s power delivery system went offline for 10-plus hours. In the days that followed, there was a lot of speculation concerning its cause. Baseless reports surfaced listing everything from sabotage to cyber-attacks. There were also assertions of too much renewable generation on the grid. Typically, blackouts are rarely caused by a single issue, but that has never stopped the rumor mill.

It's not usual for power grid problems to start out a minor hiccup that escalates into more complicated predicaments. I remember taking a power system analysis class in graduate school. The prof provided us with blocks of subroutines that we had to combine to produce a computer model for a virtual power system. Once it was operational, he supplied scenarios that required adjustments to our power system’s parameters while the grid operated. It was astonishing how easy it was to unintentionally destabilize the model by tweaking a seemingly minor variable.

Who Knew

Normally that simple adjustment should not have effected anything suddenly produced an unbalanced power system. When accepted countermeasures were applied, they had the opposite effect. They took us further down the rabbit hole. Amazingly, the professor was always there when this happened. He asked questions that no one could answer. He set us up! Our assignment, answer those question. Determine what will prevent future occurrences. It was an amazing learning experience and provided firsthand experience seeing how sensitive a dynamic power system can be, without harming anything.

Getting back to the Iberian Peninsula blackout, the preliminary findings were published in mid-June. One came from the Spanish government, and another came from the grid operator, Red Eléctrica de España. These reports provided great deal of information, and are available online for anyone wishing more details, but for our discussion let’s keep it simple. First both reports said there had been no attacks! Both also agreed that the amount of renewable generation was not a factor either.

Stress Counts

Digging into the report it said that the power grid had been stressed for several days prior to the outage. There had been unusual voltage surges and frequency oscillations on the grid. The operators followed normal procedures to stabilize those conditions, but that led to other problems. Some of the fossil-fueled power plants failed to provide the reactive power they contracted to supply. Other fossil-fuel plant’s had problems with malfunctioning automatic voltage control systems. That led them to prematurely trip offline, which led to cascading loss of other units.

The lost generation capacity reach enough gigawatts that the frequency reached the critical point of 48 Hertz resulting in the interconnections between the Iberian Peninsula’s power grid and the French power grid opening to protect the EU’s grid. These sequence of events will continue to be studied for years. It’s going to be extremely interesting when final reports become available and it’s a good bet this event is going to provide operational insights.

What's Next

These preliminary findings included many points-to-ponder for those of us operating and maintaining the power delivery systems. They discussed the need for grid modernization, more energy storage, and additional power electronics to name a few improvements. If you remember back a few months ago, “Charging Ahead” discussed ASCE’s (American Society of Civil Engineers) 2025 Report Card for America’s Infrastructure. The energy sector dropped to a D+ for its overall rating, which is going in the wrong direction for a society so dependent on a reliable source of electricity.

Since the ASCE report card came out, the task of modernizing our power grid’s infrastructure suffered some major setbacks in the form of government funding cancelations the industry has expected. Interestingly, there’s a push by DOE to extend the operational period for our aging coal-fired plants beyond their retirement dates due to growing power demands.

Google’s “AI Overviews” places the average lifespan of a thermal power plant at 30 years. It found that average age of the coal-fired power plants to be retired at about 54 years of age. It couldn’t determine the average age of coal-fired plants on the Iberian Peninsula, but said data suggests they are likely nearing or exceeding 40 years of operation. Perhaps there’s one lesson to be learned from the Iberian Peninsula blackout. Aging coal plants need to be retired for a good reason – obsolescence!

About the Author

Gene Wolf

Technical Editor

Gene Wolf has been designing and building substations and other high technology facilities for over 32 years. He received his BSEE from Wichita State University. He received his MSEE from New Mexico State University. He is a registered professional engineer in the states of California and New Mexico. He started his career as a substation engineer for Kansas Gas and Electric, retired as the Principal Engineer of Stations for Public Service Company of New Mexico recently, and founded Lone Wolf Engineering, LLC an engineering consulting company.  

Gene is widely recognized as a technical leader in the electric power industry. Gene is a fellow of the IEEE. He is the former Chairman of the IEEE PES T&D Committee. He has held the position of the Chairman of the HVDC & FACTS Subcommittee and membership in many T&D working groups. Gene is also active in renewable energy. He sponsored the formation of the “Integration of Renewable Energy into the Transmission & Distribution Grids” subcommittee and the “Intelligent Grid Transmission and Distribution” subcommittee within the Transmission and Distribution committee.

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