Timeline and key stages of the outage

The Spanish government report identifies three phases of the crisis:

• Phase 1 (12:00–12:30) – Atypical frequency fluctuations (0.6 Hz and 0.2 Hz) led to an increase in voltage. The operator applied standard measures, but they only partially stabilized the system.
• Phase 2 (12:32–12:33) – A sharp increase in voltage caused massive generation outages in Granada, Badajoz, Seville and other regions.
• Phase 3 (12:33–12:33:30) – Cascading outages due to overvoltage, loss of synchronization with France and a complete collapse of the Iberian Peninsula power system.

Main causes of the accident

The report points to the multifactorial nature of the incident:

Insufficient voltage control

• Lack of synchronous generators regulating voltage (their number on April 28 was the lowest since the beginning of the year).
• Incorrect operation of some stations that should have stabilized the voltage, but instead exacerbated the problem (for example, by generating reactive power).

Ineffectiveness of protection mechanisms

• Automatic load shedding did not work optimally, reducing consumption and further increasing voltage.
• Some generators disconnected before the permissible limits (before reaching 380-435 kV), which accelerated the cascading collapse.

Lack of flexibility in the system

• Solar and wind power plants (asynchronous sources) could have helped, but Spanish regulations do not allow them to participate in voltage regulation.
• Lack of energy storage (in 2024, Spain introduced only 250 MWh, which is extremely low for such an energy system).

Restoration of power supply

• International connections (France, Morocco) and hydroelectric power plants (Duro basin) played a key role.
• By 22:00, 50% of consumption was restored, by 7:00 on April 29 – 99.95%.

Recommendations for preventing such accidents

• Strengthening control over the fulfillment of obligations by market participants.
• Involvement of renewable energy sources in voltage management (e.g. through solar power plant inverters).
• Development of energy storage and increasing the flexibility of the system.
• Review of protective mechanisms (so that outages do not aggravate the accident).

Response of SolarPower Europe

The association emphasizes: “Solar energy is not to blame.” – Photovoltaic plants are technically capable of regulating voltage, but Spanish regulations prohibit this.

• Investments in smart inverters and storage are needed.

Conclusion

The accident of April 28, 2025 in Spain is the result of systemic problems, not a single failure. Key lessons:

1. Voltage regulation requires more resources (synchronous generators or RES adaptation).
2. Protection systems must be reviewed to avoid aggravating the crisis.
3. Spain needs to actively implement storage and flexible solutions for the stability of the power system.

This case can become a precedent for other countries, especially with a high share of renewable energy.