Power-cable failures offshore are often the main risk affecting the development and operation of offshore wind farms. Approximately 80% of insurance claims in the offshore wind industry are linked to cable failures. To reduce failure levels, DNV GL, ECN, WMC, BREM, VanderHoekPhotonics, Deltares and other partners are joining forces in a Joint Industry Project (JIP): Cables Lifetime Monitoring. 'The aim of this study is to reduce the chance on power cable failures in offshore windfarms. One of the ideas which will be developed in this project is the continuous monitoring of the integrity of power cables during the whole lifetime by advanced use of optical fibre sensors. Continuous monitoring of the cable's state of health enables early identification of possible failures', explains Jan-Joost Schouten, an offshore expert at Deltares. 'By preventing a significant number of cable failures caused by damage during manufacturing, installation and operation, we are convinced that our study will allow us to significantly reduce the levelized cost of electricity (LCoE) of offshore wind, in other words the average cost price of an electricity production unit over its lifetime. Reducing failure probabilities enhances the reliability of the energy network'.
Cable failures are one of the main risks affecting offshore wind operations because they can shut down an (important part of an) offshore wind farm for a duration of months, resulting in a financial as well as a societal impact. Despite the fact that power cables typically form only 5 to 10% of the total investment costs in an offshore windfarm, they account by far for most of the unavailability of the windfarms, and for claim costs of 100s of millions of Euros annually. In view of the development of the number of offshore wind farms, this amount will increase considerably in the future. Cable inspections and repairs are expensive maritime operations. Repairs on cables can easily take weeks or even months because of the weather or the limited available of equipment and vessels. That can severely impair revenue and also reduce the technical lifetime of offshore wind farms.
Outcomes of failure mechanisms and consequences stated in guidelines for the cable system An earlier analysis conducted by DNV GL already showed that cable failure is partly attributable to manufacturing, design and installation errors. In addition, it is known that morphodynamic processes such as sand waves can effectively expose submarine cables, which significantly increases the risk on third party damage. The knowledge regarding the major causes of power cable failures will be further enhanced by analysing the (details of) failure data of a.o. the JIP participants. This will be focused on extracting lessons learned and points for improvement for the industry. These learning points will be taken forward towards guidelines for improvements in design, manufacturing, installation and operation of the submarine cable systems, towards new verification protocols that can ensure that failure causes are not part of a submarine cable project anymore, and towards new monitoring systems. To illustrate the latter, within the project, a monitoring system will be designed and developed to monitor the health of the cable during all stages of the cable lifetime. In addition, we will quantify outage costs caused by cable failures to obtain financial key-figures.
The project runs from mid-2018 to mid-2020. The results can be applied to both existing and future wind farms as well as for other submarine cables, like interconnectors. The partners in this project expect to be able to reduce the LCoE, insurance costs and the CO2 footprint of the offshore industry by increasing the reliability of offshore wind energy.
It is still possible for developers, network operators, investors, insurance companies, cable manufacturers and installers of offshore wind farms to participate in the project.
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