Cables: The wind farm's lifeline
Cables form the lifeline of the DanTysk wind farm. They ensure that the energy produced at sea via the wind turbines can be transported to the substation. It is what the experts call 'internal farm cabling'. Energy is transported from the offshore substation to the converter station via a high-voltage cable supplied by Tennet, the network operator.
In addition, a submarine and onshore cable, approximately 205 kilometres in length, will transfer electricity from the converter station to the substation in Büttel, close to the area of Brunsbüttel, where it is fed into the German extra-high voltage grid.
Robust cables with 'a precious core'
Submarine cables need to have an extremely robust build so that time-consuming maintenance work can be reduced to an absolute minimum right from the outset. A steel wire sheath with an external plastic coating protects the 10 to 14-centimetre-thick cables against mechanical damage. The copper cables installed in the DanTysk wind farm will include three separate sections; these will be bound together, along with a fibre optic cable and an insulating layer, to form the overall submarine cable. The fibre optic cables enable data exchange between the turbines and the substation during operation. They also make it possible for the turbines to be controlled and monitored remotely from the control centre in the Danish town of Esbjerg.
Cable vessel lays the Inter Array Cables
The inter array cable network will connect the 80 turbines with the offshore substation. The installation of 88 cables with a total length of approximately 111 kilometers is performed by Visser & Smit Marine Contracting and conducted by the cable-laying vessel Olympic Taurus. The vessel represents a new generation of environmentally friendly and operational state of the art multipurpose vessels, where much attention is put on fuel economy and low emissions. It is fitted with a carousel and quadrant for cable lay operations.
Pull-in procedure with cable protection system (CPS)
The cable protection system by Tekmar is mounted on the cable end before the pull-in to assure the cable will not get damaged during the pull-in. The pull-in wire is attached to the pull-in head and in order to avoid damage by too much tension, a weak link system is used. This weak link will break at a pre-defined load of several tonnes. After it has been confirmed that the CPS has latched inside the entry hole of the monopile, the weak link between the pull-in head and the CPS will break. This allows the cable to run through the CPS and be pulled further to the Foundation’s electrical cabinet for connection to the Wind Turbine Generator.
Cable burial with Canyon’s trencher T750
The cables will be buried 1,5 meters under the seabed to reduce the risk of cables being damaged and minimize the impact on the environment. A trenching ROV (remotely operated vehicle), the Maersk Lifter, will bury the cables in order to avoid the need of divers.