Repairing damaged cables at already operating offshore wind farms such as the UK's Race Bank, or boosting inadequate protection systems elsewhere, will cost Orsted about DKr3bn ($489m), chief financial officer Marianne Wiinholt revealed.

“We found out a short time ago that we had cable failures at one of the array cables at Race Bank,” Wiinholt said during a media call on first quarter results.

“When we investigated the cause of that, we found that more cables were damaged.

“The damage is caused by the fact that the cable protection system, which is both from the turbines and links to the cable, is placed on top of rocks. With the movement in the sea, this cable protection system gets damaged.”

Orsted previously wasn’t aware of the issue that it believes affects about 10 of its offshore arrays as the cable protection system it was using at the time was industry standard, she added.

“To a large extent we will be able to mitigate it through stabilising the cable protection system. It will be done by dumping rocks on top of the rocks that are already there.”

At other wind farms, the cables are so damaged that the company will either need to repair or replace them, which is more expensive than dumping more rocks on top of the existing protection layer.

To avoid further damage, Orsted will carry out two campaigns. A first one placing more rocks on existing cable routes will be done this year, while the company until 2023 will carry out more seabed surveys to see which cables need to be repaired or removed.

The first quarter of this year was already impacted by a DKr0.8bn warranty provision related to cable protection system issues.