Wind Energy – Cable Repair
Approximately four months on from the failure of the cable which connects the Rentel wind farm to the mainland, the repair work has now been completed.
The fault was located just below the Rentel transformer platform. A new section of cable, approximately 400 metres long, was attached to the platform and connected to the existing cable under the seabed.
The four connected wind farms were still able to generate electricity throughout the repair work, because they are part of the meshed offshore high-voltage grid (via Elia’s MOG or offshore power hub). Their electricity output was capped slightly during periods of very high winds to prevent the operational export cables from being overloaded.
Despite this, offshore and onshore wind energy production was very high in the first few months of this year.
On 9 January, the MOG cable connecting the Rentel platform to the mainland suddenly failed. The fault was located at the spot where the cable enters the high-voltage platform. Carrying out repair work at this location was very challenging and complex.
The high-voltage platform is 34 kilometres off the coast and the past few months have been particularly windy. 400 metres of damaged cable were replaced. Special lifting techniques involving ships were used to lift the cable from the seabed. However, such methods could not be adopted just below the platform, so divers had to disconnect the cable.
Connecting the new and existing cables was also challenging. To do so, an offshore rigid joint was used that was repositioned on the ground 30 metres below sea level. This operation could only be performed during an extended period of low wind, so the repair work had to be postponed for some time. A platform joint also had to be installed on the platform.
All parties involved (Rentel; NTK, the cable manufacturer; and Elia Transmission Belgium) were able to safely and smoothly work together amidst difficult circumstances.
“We very quickly realised that this was going to be a challenging repair operation given the timing and exact location of the fault. It is only due to the perseverance, expertise, flexibility and knowledge of all staff and our partners that we were able to complete the repair work within just a few months,” said Geert Moerkerke, Head of Assets Offshore Elia Transmission Belgium.
“We are immensely grateful to Elia’s staff for the way they handled the situation. The repair work posed an unprecedented challenge to all teams involved, requiring them to work under quite extreme conditions at critical times. Thanks to the MOG, all connected wind farms continued to generate electricity throughout the repair work – something that makes a world of difference at this (windy) time of year,” added Mathias Verkest, CEO of Otary.
