Absolutely. The infrastructure is very fickle, but also enormous on the scale of countries.

Since we're talking about hypotheticals, I could say these things are also true:

1. There are counter-drones deployed and patrolling air space above the towers.

2. There are hundreds of independent power lines with 2N redundancy, so cutting 5-10 high voltage lines would do nothing.

3. The undersea cable points are protected by state agents and have good security for amateurs to compromise.

4. Europe will have 24-48 hours worth of storage even if ALL the lines are cut from the Solar Generation plants.

5. Europe will have backup power generation capacity in the form of locally stored and operated fossil fuel plants.

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In other words, there's absolutely no evidence that the future hypothetical solar installation is going to be more vulnerable than the infrastructure that already exists today, and surprisingly Europe doesn't plunge into darkness every week.

I don't think the main problem here is random terrorists cutting power to Europe by blowing up a power line tower. The real problem is that nation states that control the Sahara haven't proven to be stable (Syria, Egypt), or don't always have great relationships with Europe (Algeria in the 90s).

As to points 4 and 5, although storage and some backup capacity is reasonably feasible, this would mean that Europe could very well be forced to go to war in short order to get their full power supply back if a rogue organization gained power in North Africa.

It might motivate Europe to improve relations with the region

We'll be better off building nuclear reactors, thank you. The social and political challenges are much lower and so are the risks.

(I obviously meant Libya, not Syria)

Burry the cables. Won't protect you from everything, but makes it a bit harder to compromise them. You can even have "cages" around them that alarm a nearby response team of any manipulation. Of course, this adds siginifcant cost, but then you have to take the total economical cost into account if an attack is successful.

Damage that takes a few hours to fix is not going to destabilize a country. If you can scale it to keep up 24/7 disruption you already have an army and far more useful approaches like destroying ports.