Offshore staff
LONDON – The Offshore Wind Accelerator (OWA) has published recommendations for fiber optic cable design to lessen the risk of export cable failures.
These are based on the conclusions of the Fibre Optic Cable Protection Assessment project managed by the Carbon Trust and funded by OWA partners EnBW, Equinor, Ørsted, RWE, ScottishPower Renewables, Shell, SSE Renewables, and Vattenfall Wind Power.
In 2017, the UK’s Offshore Wind Programme Board published a review of high voltage export cable reliability. This revealed that for issue in the fiber optic cable accounted for six of the seven post-commissioning failures the UK offshore wind industry had at that point experienced.
Each failure incurred an estimated cost of just under £23 million ($32 million), in terms of the repairs and the loss of wind farm energy production.
Ørsted and Nexans then initiated modeling to investigate the mechanism of failure, identifying the fiber optic core as the cause. This led to the recent project, conducted by engineers at RINA Tech UK.
Main recommendations include:
1. Optical fibers should be covered by a stainless steel tube and stainless-steel wire armor, with a combined resistance of no less than 30Ω/km.
2. The fiber optic cable sheath should be semi-conductive, with a material resistivity no greater than 1000Ω∙m, and dimensioned so that the radial resistance through the sheath is not more than 75Ω∙m.
3. No insulating binder tapes, adhesives or other insulating material between the armor wires and sheath of the fiber optic cables.
4. The three-core cable should have extruded fillers made from semi-conducting material, or a semi-conducting section around the channel for the fiber optic cable.
These suggestions will likely increase the cost of the export cable between 0-0.5% depending on the design that it replaces, but should not affect the installation cost.
02/12/2021
