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.
[1] https://www.ree.es/en/ecological-transition/electricity-inte...