Estlink 2 cable fault caused by internal short circuit

The failure of the Estlink 2 undersea electricity cable was caused by an internal short circuit that may have been created by the position of the cable.
Estlink 2, which runs between Estonia and Finland, suffered a failure at the end of January.
500 meters of the submarine cable will be replaced and most of the repair work will go into rectifying the mistake. The work is expected to end in August.
The fault is on the Estonian side of the cable around five to 10 meters inland, and approximately seven to eight meters below ground.
"And what makes the nature of the fault extremely complex is the very fact that it is at the boundary between the sea and the land," Elering board member Reigo Kebja told Monday's "Aktuaalne kaamera".
Due to its location, the fault took several months to find. Elering said the problem was not man-made and could have been caused by the geological conditions at the site.
"The difference in height between the top of the step where the cable starts to go out to sea and sea level is about 25 to 30 meters. Today, we suspect that the soil layers have shifted in this range to such an extent that the cable has been damaged," said Kebja.
Jako Kilter, professor of power systems at TalTech, said cable failures are inevitable.
"The cable is a technical element and with these technical things small failures do happen. Either the insulation of the cable does not hold up, or there is some kind of internal damage," the professor said. "A submarine cable is certainly more complex, it's more difficult to repair afterwards."
In the case of the Estlink 2 failure, the 45-degree inclination angle, which makes the cable installation especially critical, could have been fatal.
Kilter said the straighter a cable is laid "the better" as any angles are "bad".
"How the cable was installed certainly plays a part. It could also be that cables are sensitive to all kinds of non-standard tensile forces or how it was handled when it was installed," he said.
With a capacity of 650 megawatts, EstLink 2 was officially launched in 2014. The 350 MW Estlink 1, which will also connect the Estonian and Finnish electricity systems, is currently in operation.
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Editor: Merili Nael, Helen Wright
Source: Aktuaalne kaamera