It looks like the Iberian peninsula is relatively isolated from the rest of the CESA synchronous grid, with only 2% cross-border capacity compared to local generation. [1]
There's a map at [2]
> The Spanish electricity system is currently connected to the systems of France, Portugal, Andorra and Morocco. The exchange capacity of this interconnection is around 3 GW, which represents a low level of interconnection for the peninsula. The international interconnection level is calculated by comparing the electricity exchange capacity with other countries with the generation capacity or installed power.
That graph doesn't seem to make a very clear distinction between historical, real-time and predicted values... I think the event happened at 12:30 local time or so.
There seems to be some kind of recurrent daily pattern where the French - Spanish interconnect switches from Spain -> France imports to France -> Spain exports at around that time, and then back again in the late afternoon.
There's a map at [2]
> The Spanish electricity system is currently connected to the systems of France, Portugal, Andorra and Morocco. The exchange capacity of this interconnection is around 3 GW, which represents a low level of interconnection for the peninsula. The international interconnection level is calculated by comparing the electricity exchange capacity with other countries with the generation capacity or installed power.
[1] https://www.ree.es/en/ecological-transition/electricity-inte...
[2] https://www.entsoe.eu/data/map/