Since the end of September TenneT has been working hard to get the COBRAcable up and running as soon as possible after a defect in the cable was discovered.
We first investigated whether the failure occurred onshore in or around the high-voltage substation. This turned out not to be the case. We started the first indicative measurements from land. We do this with special equipment in which a tone or a pulse is sent through the cable to investigate where approximately the defect is in the cable. Then a vessel sailed out close to the suspected fault location to send another tone or pulse through the cable to determine the exact fault location. It also needed to be determined whether an internal or external cause has caused a defect.
At this moment, a team is working at sea from a ship. The cable is cut at a depth of 40 metres on the seabed and lifted up. On both sides of the cut cable, the cable is measured 200 metres long to find the exact fault location(s). As soon as this has been done , more can be said about the recovery operation in the next weeks based on the new weather forecasts.
For the repair operation, the piece of cable where the fault is located will be removed and a new piece of cable will be installed and reconnected to the cable. The cable will then also be tested immediately. If the test is successful, the cable will be laid back on the seabed and finally buried at a depth of 2 metres in the seabed.
Everything depends on the weather. We hope that the COBRAcable will be operational again at the beginning of 2021. TenneT has organised everything to meet this schedule. But that requires good weather at sea.