Iberian Grid Stability Atlas

Cascade Sequence · 12:32–12:33 CEST

12:32:00 – 12:32:48

Peninsula-wide

Large renewables (>5 MW) shed –500 MW in 48s during schedule adjustment. Fixed power factor mode injects reactive ramp into transmission.

12:32:57 · Event 1

Granada Province

PV generation trip: –355 MW. Voltage begins rising in southern Spain.

12:33:16 · Event 2

Badajoz / Extremadura

PV + CSP cascading trip: –727 MW. Overvoltage exceeds 435 kV. Shunt reactors available but not activated.

12:33:18 · Event 3

Sevilla Province

Third cascade: –550 MW. Five further provinces lose –928 MW in 2 seconds. Loss of synchronism with European grid at 12:33:21.

Spain–France NTC Constraint

Avg. utilization rate 2025

78%

Congestion 34.3% hrs (FR→ES) / 27.5% hrs (ES→FR)

Operational NTC capacity

2,800 MW

Baixas–Santa Llogaia (2015). Eastern Pyrenees only.

Bay of Biscay HVDC (proposed)

+3,000 MW

Onshore route agreed. Physical escape valve — not available on April 28.

Map Layers

400 kV Transmission

Primary grid trunk routes

220 kV Transmission

Secondary corridors

Solar / CSP Generation

Installed capacity clusters

Wind Generation

Onshore capacity clusters

Reactive Power Deficit Zone

Extremadura–Andalusia corridor

Failure Event Nodes

Cascade sequence · Events 1–3

Spain–France Border

NTC saturation annotation

Bay of Biscay HVDC

Proposed route (not operational)

28 April 2025 · 12:33 CEST

First overvoltage-driven blackout in history