While cable faults will happen, in the UK we’re learning ever more about how best to mitigate and manage this risk. In the run up to #Cables19, John Price, Group Business Development Director at EDS HV, details how emerging offshore wind markets are learning from our experiences.
There are three main areas where cable faults are likely to occur; manufacturing, installation and in-service.
The first of these, manufacturing, now carries the least amount of risk as standards have been improved and adapted to subsea requirements.
Alongside industry recommendations, new standards are being developed which, provided the standards and qualification process has been followed and the correct materials used in fabrication, should mean that a cable won’t generate a fault as a result of the manufacturing process.
It’s one thing to say you have a product that can reach these exacting standards but quite another to have robust manufacturing processes and procedures in place to ensure they are met. A manufacturer must make sure their factory is optimised for each step of the manufacturing process, adequate storage capacity is available, the right testing requirements are set up and load-out facilities are correctly designed for the vessels collecting cable. Provided all of these are considered and managed correctly, there shouldn’t be any significant issues relating to the manufacturing for the latest cables.
Installation was at one point considered the greatest risk to faults on cables. This was down to a lack of knowledge and not incorporating lessons learnt in the industry by some of the installation companies. In years gone by problems ranged from using static barges, to poorly designed Cable Protection Systems (CPS) and lack of knowledge of the seabed soil conditions and cable routing.
However, the industry in the UK is now becoming more mature and installation companies and developers are fully aware of these risks. Major investments have been made, and installation vessels are far better suited to the requirements of cable installation, CPS designs have improved, and more detailed assessments are made of seabed and soil conditions. It’s impossible to remove all the risk from the installation process. Cables are being physically moved into position and buried which inherently involves some risk, but the latest techniques mitigate these risks to a minimum.
The final area where faults can occur, and the one which is probably the least addressed, is in-service. At EDS, we believe this category needs the most attention going forward.
Cables are buried in precise locations and at precise depths. However, it is a hazardous environment. Moving sands, ocean waves and shifting seabeds or even external interference - such as vessel anchors or fishing nets - mean that cables will not always remain buried at the designated depth. Up to now, annual or bi-annual route surveys have been carried out to assess any movement and cable burial changes, however, it is becoming more widely recognised that this is not an adequate solution. Checks on this basis are too infrequent and the risk of fault between checks is too high. As a result, the industry is now needing solutions that offer constant assessment of a cable’s performance.
At EDS, we believe a fleet of systems is vital to determine cable performance, potential fault and fault location - these systems include temperature sensing, strain monitoring and Distributed Acoustic Sensing. Using DAS for continuous monitoring of a cable means that should a fault occur; the location of the fault can be easily pinpointed within a 10-metre distance. That level of accuracy means significant time and costs can be saved compared to using remote-operated underwater vehicles and GPS to locate the fault.
Linked to this should there be a fault, is having the ability to repair the fault should it be needed. Many companies are now also looking into how to better manage spares by holding stocks of universal joints that can be used across different wind farms - rather than having specific spares for each wind farm which need to be ordered and stored by the developer.
We believe the key to unlocking all of these innovations is Big Data. The ability to capture large amounts of data from the wind farm which is then analytically assessed to provide algorithms may in time provide the ability to determine the exact location of seabed movement, the effect this will have on the cable performance and the likelihood of a fault occurring and if so, when.
Faults will continue to happen as risks in the offshore environment can never be fully mitigated. But by analysing and learning from our experience in the UK, we are better able to manage risk and optimise performance, and if we apply this knowledge base from the UK to new markets developing offshore wind, these markets will be able to manage risk and mature better and faster.