The cables are well-protected, but if they are damaged - same as with HV overhead lines - there is protection circuitry on both sides that trips and shuts off the power. So it will limit the damage to the rest of the grid, but you probably wouldn't want to be scuba-diving next to the cable when that happens.

Underwater high power cables are a mature technology. The operators would have equipment distributed across the line to monitor the cable. Any shorts or opens would be detected and breakers would be used disconnect the section of the cable.

also, what's stopping an antagonist from severing the cable?

Unrelated but fun story about antagonists and undersea cables that I saw in some Cold War history book in college.

The CIA had cooked up a bonkers covert mission to send a submarine with an airlock right into the soviets’ top submarine harbor. There, divers were to place a tap an underwater data cable that fed the nearby submarine base—a crown jewel of Soviet sub deployment intel.

The CIA knew the cable passed through the harbor somewhere. But where?

To search the entire harbor for a tiny cable would have taken too long. The mission planners were stuck on this problem until one day one of the CIA planners is out on his personal boat. He sees a sign that says “WARNING: Undersea Cable” and has a moment of clarity.

They brought a translator, popped up the periscope in the Soviet harbor, and spotted an equivalent sign which they used to carry out the mission successfully.

For extra credit they had to go back to exfiltrate the data if my memory serves.

I think you're misremembering the part with the signs. The guy came up with the idea to look for a sign on the beach that forbids anchoring. They found it and the cable proved to be there. Source: https://en.wikipedia.org/wiki/Blind_Man%27s_Bluff:_The_Untol...

It sounds like you're right. Also, that's the book I read way back then! Neat, I'll have to pick it up again.

Operation Ivy Bells https://en.wikipedia.org/wiki/Operation_Ivy_Bells

>The large recording device was designed to detach if the cable was raised for repair.

Clever!

Same thing that is stopping them from cutting other power lines: laws, and punishment for breaking those laws.

I mean countries in time of war. Presumably that is one of the Emergencies for which this cable is intended.

No, not really. In a war footing, the power plants themselves would likely be targets; the cables are fairly irrelevant. This sort of interconnect lets spikes in consumer demand get smoothed out.

The cables are extremely relevant: it is far harder to protect hundreds of kilometres of underwater cable, of which any part can be cut by a difficult to detect submarine, than it is to protect power plants.

No there's really no way to protect civilian power plants against modern stand-off weapons. It's just impractical at any reasonable cost.

There is no such thing as a perfect defence, against an enemy with unlimited resources. But it is much more expensive to attack an enemy's power plants with $1 million cruise missiles than it is to cut their underwater cables by dragging anchors over them. Also, you can plant bombs on underwater power lines and set them off later - that's a huge problem re: how much energy capacity could go down at once.

Anyway, we definitely can protect installations from stand-off weapons: CIWS systems like the Phalanx can shoot them down these days, and they're relatively cheap. It's not perfect protection - eventually one will get through - but it does raise the cost of a successful attack substantially.

The cables aren't critical, though. They're nice to have for peacetime, but given it hasn't happened yet it's clear each nation is able to at least function without them. In a war, there'll be bigger concerns than "everyone turned on their AC in Israel and we'd like to buy energy from Greece".

One of the biggest goals of the many undersea cable projects around the world is to enable much higher dependence on unreliable renewable power. They may not be critical yet. But they will be.

It, and any kind of infrastructure, would be a prime target - assuming that is what they want. But infrastructure represents value, destroying a country's powergrid and connections like that is only a thing if your aim is complete destruction.

Ideally, in war, you destroy their military, or at least damage it enough for the other party to concede and discuss peace terms, and leave the rest alone.

WW2 was, I believe, the last war where they went for complete destruction of infrastructure, industry, and civilians. The Allies firebombed Dresden and nuked Hiroshima and Nagasaki. It is estimated that 50-55 million civilians died in WW2, of which part due to disease and famine. No conflict since has had that high a civilian casualty rate.

Israel has the means to detect and prevent such shenanigans.

The same thing that's stopping them from cutting the under-ocean internet cables, I imagine - political and military repercussions.

The armed forces of these nations.

not across 1,700km

They dont have to directly prevent them, just you know, shoot anyone who tries after the fact.

Military is a deterent because of the threat of retalitation, not because they literally prevent other countries from doing things in the moment.

1700km is fuck all. 2 hour flight for commercial airliner, less for pointy aeroplane. even eurocopter can go 300-400 kmh, not a problem

1700km underwater?

The navies of these nations, then.