The Cable JIP is a TKI Wind op Zee research project for floating wind solutions and electrical power offtake cables. The project aims to de-risk electrical cable installations for a deep draught TLP floating wind solution, by understanding and validating the power cable’s behaviour in tank and model tests.
The JIP examines the forces and motions of dynamic cables in extreme (storm) conditions, as well as wind turbine induced fatigue, floater induced fatigue and Vortex Induced Vibration. Subsea cables may be responsible for 80% of failure cases in the renewable energy industry. For static cables, the main hazards result from human activities. Failures of dynamic cables are less well understood and are presently subject to investigation. Failure of dynamic offtake cables can result in significant loss of revenue for the operator.
The Cable JIP is executed and managed by MARIN, Bluewater and Twentsche Kabelfabriek (TKF).
The following conclusions have been reached by the CABLE JIP research project:
- Based on systematic design variations, a simple catenary design was selected for the electrical cable, having a low maximum tension, a relatively large bending curve near the touchdown point and the smallest possible movements near the touchdown point;
- A fully coupled time-domain simulation model was developed for the OD 117 mm cable, including the motions of the TLP, the forces of the mooring system and a FAST model for the wind turbine;
- The ultimate limit state of the OD 117 mm electrical cable was established for severe weather conditions in 96.5 m water depth, significant waves heights of Hs 11.4 m and current conditions up to 1.8 m/s.
- A fatigue limit state of more than 18 years was calculated for the scatter diagram, taking into account a lifetime safety factor of LSF 10;
- The calculated fatigue life is a for the standard lay-out of the OD 117 mm electrical cable with plain aluminium sheathing for water barrier around the conductor cores. Follow-up work has been started to investigate possible improvements of the fatigue life when using corrugated aluminium sheathing.
- At this stage of the project, only the fatigue damage resulting from the FOWT motions and the direct wave-induced motions of the cable is considered. Fatigue damage resulting from VIV was omitted at this stage.