On April 28, 2025, one of Europe’s largest power outages impacted millions across Spain and Portugal. This blackout offers vital lessons in modern grid resilience, especially under high renewable penetration. Let’s explore the sequence of protection-related events and what they reveal about the future of power system design and stability.
- The Iberian grid lost ~15 GW of generation (~60% of demand) at 12:33 PM CEST.
- Two generation trips occurred back-to-back, triggering a major frequency drop.
- Grid separation from France followed due to protection relay operations sensing inter-area oscillations.
- The Low inertia and high PV share (~59%) made the grid vulnerable to instability.
- Inverter-based solar tripped under under-frequency conditions, worsening the collapse.
- Relay operations at substations triggered immediate generator isolation.
- Out-of-step relays on 400 kV France - Spain lines activated to prevent continental spread.
- Under-Frequency Load Shedding (UFLS) acted but could not stop the cascading failures.
- Result: Total loss of synchronism, voltage collapse, and system-wide blackout.
- Coordination of protective relay settings is critical in the high renewable grids.
- Synthetic inertia and fast reserves are essential to buffer sudden losses.
- Grid islands must be equipped with robust frequency and voltage control mechanisms.
- Real-time phasor monitoring is necessary to detect and act on oscillations early.
This event underscores the importance of adaptive protection, enhanced control schemes, and cross-border coordination. As renewables continue to grow, system operators must modernize relay settings, improve modeling of dynamic events, and ensure defense-in-depth strategies.
- Red Eléctrica de España (REE), official communications and grid data, April 2025.
- Reuters (2025). 'Massive blackout hits Spain and Portugal'.
- Euronews (2025). 'Blackout disrupts the Iberian Peninsula'.
- El Diario (2025). Technical analysis of blackout and protection failures.
- ENTSO-E & RTE, Interconnection event data and oscillation records.
- LinkedIn technical commentary by European grid protection engineers.
- Infobae (2025). Clarification on solar generation loss and atmospheric conditions.
Good article. What relay coordination are you refering to specific to this event, the relays operated with no issues based on the reports.