Update |
490 480 470 460 450 440 430 420 410 400 390 380 370 360 350 340 330
12:32:50 12:32:55 12:33:00 12:33:05 Carmona (ES) – frequency 12:33:10 12:33:15 Time [UTC+02] Bassecourt (CH) – frequency Upper voltage limit (435 kV) Carmona (ES) – voltage Lower voltage limit (360 kV)
Evolution of frequency and voltage in the Carmona substation (Spain) and frequency in the rest of continental Europe (Bassencourt substation, Switzerland) during the incident. Data source: Red Eléctrica, Swissgrid. Image: ENTSO-E
Events between 12:33:19 and 12:33:22 CEST The automatic load shedding and system defence plans of Spain and Portugal, elaborated in accordance with Commission Regulation (EU) 2017/1485 (2 August 2017), were activated but were unable to prevent the collapse of the Iberian power system.
Event at 12:33:21 CEST
The AC overhead lines between France and Spain were disconnected by protection devices against loss of synchronism.
Event at 12:33:24 CEST
All system parameters of the Spanish and Portuguese electricity systems collapsed, and the HVDC lines between France and Spain stopped transmitting power.
Rate of Change of Frequency (RoCoF) in the moments before the blackout remained bellow
35 000 30 000 25 000 20 000 15 000 10 000 5 000 0
1 Hz/s up until 12:33:20.400, when the frequency was already around 49 Hz. After that, the value of RoCoF exceeded 1 Hz/s.
Restoration process
Following the blackout, each impacted TSO immediately activated its respective system restoration plans, elaborated in accordance with Commission Regulation (EU) 2017/2196 establishing a network code for dealing with an electricity emergency and restoration , as well as any other relevant procedures and protocols for restoring the voltage of the electricity system, the Expert Panel notes.
Power system restoration in some regions of the Portuguese and Spanish systems was facilitated by, among other things, activation of power system resources such as black-start capabilities in certain power plants, as well as by the existing interconnections with France and Morocco.
0:00
-5 000 -10 000
Nuclear Hydro
France IMP Portugal EXP Combined cycle
Wind
Portugal IMP PSH consumption Coal
Solar photovoltaic
Morocco IMP Balearic link
Cogeneration & EfW Thermal solar France EXP
Demand
Thermal renewable PSH generation Morocco EXP
Recovery: generation mix and power consumption in Spain, 28 and 29 April, MW Image: ENTSO-E
10 | July/August 2025|
www.modernpowersystems.com 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00
35 000 30 000 25 000 20 000 15 000 10 000 5 000 0
-5 000 -10 000
The rapid restoration of supply demonstrated the preparedness and efficiency of the affected TSOs, Red Eléctrica and REN, says the Expert Panel, with support from and collaboration with the French TSO RTE, as well as the Moroccan utility ONEE. According to the Expert Panel, this was made possible by the joint work and co- operation among TSOs developed over the years, both between the control centres and within ENTSO-E. In addition, the real-time monitoring of the status of the European electricity systems and co-ordination among TSOs made use of the European Awareness System platform, a tool developed by all TSOs within ENTSO-E.
12:33:20 12:33:25 12:33:30
50.1 50.0 49.9 49.8 49.7 49.6 49.5 49.4 49.3 49.2 49.1 40.0 48.9 48.8 48.7 48.6 48.5 48.4 48.3 48.2 48.1 47.9 47.8 47.7 47.6 47.5 47.4
12:33:35
What was the role of inertia, or lack of it, in the Iberian blackout?
ENTSO-E says this question is being assessed as part of the investigation by the Expert Panel, but “preliminary data indicates that on 28 April, the Iberian system was operating with sufficient reserves to manage usual imbalances between generation and demand.” Red Eléctrica’s June report on the
blackout was quite clear on this point: “The inertia of the system in this incident is irrelevant, since the system was already condemned by the massive loss of generation.”
According to Red Eléctrica, just before the blackout, the “system’s inertia value was higher than the ENTSO-E recommendation”, with connected power plants “sufficient to meet demand, provide inertia, enable energy flow control, and offer resources for dynamic voltage control on the transmission grid.”
Voltage (kV)
Frequency (Hz)
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