Smart Grid Disruption

1. What Happened?

On April 28, 2025, a massive blackout affected much of Spain, Portugal, and even parts of southern France. The grid collapse began at 12:33 CEST when an overvoltage event near Zaragoza initiated a chain reaction of disconnections that cascaded through the transmission network. (1)

Within moments, the Iberian Peninsula lost around 15 GW of electricity supply, accounting for approximately 60% of total load – it suddenly went out in a few seconds, including due to the disconnection of solar farms. (2)

A preliminary report from Spain’s Ministry for the Ecological Transition and the Demographic Challenge (MITECO) confirmed that the cause was not a cyberattack, terrorism, or weather-related disruption—but rather an uncontrolled electrical overvoltage (3) and current balancing problem with  a series of misconfigured protections and automated grid responses. (4)

Situation in Spain and Portugal and the impact of the outage: Both countries experienced widespread disruptions: elevators, subway lines, cash register systems, refrigeration equipment, industrial facilities, and even internet services came to a halt—before they were finally plunged into darkness as the lights went out. (17)

2. Root Causes and Systemic Failures

➤ Overvoltage Trigger and current balancing problem

A sharp increase in voltage occurred after a fault in the Aragón region. The voltage rose above the tolerance level of multiple assets in the national transmission network.

This generated an overproduction situation and overvoltage that the network could not compensate for. (5, 6)

➤ Cascading Protection Responses

Rather than containing the incident locally, protective relays in multiple substations triggered immediate shutdowns, failing to isolate the fault. 7  These settings were overly conservative, lacking sufficient coordination with modern renewable-heavy grid dynamics.

So, the automatic protection systems of the network sequentially shut down a significant part of the generating capacity (lack of reactive power absorption), which led to a chain reaction collapse. (1)

France disconnected from the grid to protect its own system, causing isolation in the Iberian Peninsula. (8)

➤ Lack of Real-Time Flexibility

A key finding in the Smart Energy International article is that the system lacked real-time voltage regulation capacity, and dispatchable reserves were insufficiently activated—especially critical as much of the generation mix was from intermittent renewables. (9)

➤ Summarization

A series of events spanning several sectors: solar panel failure → surge → automatic shutdown of generating units → sudden grid collapse. The system did not have sufficient reserve capacity or inertia to compensate for short-term disturbances. Improvements are needed in terms of tracking capability and grid stability. (10)

3. Responsibility aspect

Who are responsible?

According to the Spanish government’s investigation, Red Eléctrica de España (REE) did not properly maintain the network reserve  (7) — several conventional power plants that should have been used to absorb the surge were also shut down. The large electricity provider companies did not fulfill their reactive power absorption obligations well.

The origin of the voltage fluctuation was previously linked to solar farms, but it was not an intentional excessive share of renewable energy sources, but a combination of operational errors and automated shutdowns. (4)

Consequences and causes

Network automations were oversensitive, several devices were disconnected at the same time. Due to low network inertia, the oscillations could not be handled. (11)

Security protocols were not updated to the changing system operation due to the inclusion of new, renewable energy. (12)

The cascading disconnects (disconnecting large generating units) caused the entire system to collapse disrupting everyday activities and services. The power outage also caused Internet outages across the peninsula.

Was the Iberian blackout close to having an impact on the whole of Europe?

Fortunately, no, multiple protections prevented a collapse in other countries.

➤ Immediate shutdown of protection mechanisms

Spain was disconnected from the common European power system, which is connected to France – and therefore to continental Europe – due to synchronization problems, so when the fault occurred, the relay protections immediately recognized this and disconnected the transmission lines between the countries to prevent further chain reaction effects. (13, 2)

➤ Synchronous area protection

The French and European power grid system did not allow the instability to spread further – after the disconnection of the Iberian Peninsula – because synchronization was stopped and the faulty section was isolated. Therefore, the fault did not affect the German, Czech or other Central European networks. (14)

➤ European grid redundancy and inertia

The continental system is stronger, has more transmission paths and synchronous generator reactive capacity, and was able to absorb the impact of the energy shock. (15)

4. Impact and Restoration Timeline

It was not only nice but also great work, and it was completed in a relatively short time!

• Immediate blackouts occurred across Madrid, Barcelona, Lisbon, and surrounding regions.
• Emergency power and grid-forming sources—especially hydropower and interconnectors—played a key role in recovery.
• 50% of the grid was back online within 10 hours, and full restoration (99.95%) was completed by early morning on April 29. (16)

5. Key Takeaways and Strategic Lessons

6. Implications for Grid Modernization

The blackout sent a clear message to regulators and utilities:

• Modern grid planning must include voltage flexibility, not just capacity.
• Advanced substation automation and reconfigurable relays are essential to avoid cascade failures.
• Energy storage, grid-forming inverters, and dynamic load control are no longer optional—they are strategic infrastructure.
• Utilities must integrate Industrial IoT, real-time telemetry, and smart metering data into grid decision-making.

Conclusion

The power outage described above was an unprecedented event in Europe—an entirely new phenomenon.

It demonstrated that a global technical problem within a shared and distributed power grid, operating on a common backbone network that transcends national borders, can only be managed safely if every participant looks beyond their own segment and acts in a coordinated, collective manner.

The same applies to renewable energy islands connected to the grid and traditional power networks and providers: closer cooperation and more comprehensive planning will be essential in the future.

This incident also underscored the importance of continuous, consistent monitoring, as well as proactive planning for service providers, operators, and maintainers.
With increased attention, investments in infrastructure, and organizational improvements, similar crises can hopefully be prevented—particularly in a service sector already facing significant challenges.

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