Meet Andy Readyhough, Brand Ambassador for the UK.

Andy knows the offshore wind submarine power cable transmission market inside out, having seen first hand how the industry moved from oil & gas to renewable energies and combined with the telecom submarine cable industry has defined the current offshore wind cable industry standards. It was long overdue that we needed to share with our network a droplet of his insights. 

Andy, can you tell us more about who you are?

I am a master mariner by profession having sailed in command of various vessels in my offshore career. I started my journey offshore as an apprentice to become a deck officer back in the 1980’s at British Petroleum on their tankers followed by employment in the Royal Fleet Auxiliary on their support ships for the Royal Navy, the cruise sector, the ferry sector and by far the most interesting and enjoyable the submarine cable installation & repair sector.  I came ashore in 2009, metaphorically ‘swallowing the anchor’ as they say.  My shore based career commenced in the planning of submarine cable installation and maintenance projects, initially for telecoms projects before concentrating on power transmission for renewable energy zones and interconnectors.  My roles broadened out to management of operations and latterly business development for submarine cable installation and maintenance ultimately starting my own consultancy business at the end of 2017. 

In 2020 I joined the Marlinks team as Brand Ambassador for the UK market to champion their services and support the development of the company in the established and emerging markets for submarine power cable integrity monitoring.

How have you seen the UK offshore wind market evolve throughout your career?

Offshore wind only started in the nineties, when the first wind farm was built in Denmark. The UK followed ten years later, constructing its first offshore wind farm in 2000. The early wind farms were rather small demonstration windfarm near shore. However with each round of sea bed area allocations the UK has released from then on, the size of wind farms has increased. In such a new market, it was necessary that renewable energy developers felt incentivized to start investing in offshore wind. By implementing a feed-in tariff system that evolved into the current contract for difference scheme that provides a form of financial security where offshore wind developers are paid a flat rate for the electricity they produce over a 15-year period, this allowed both developers and the associated supply chain to invest in innovation. We saw the size of generators go up, which led to less turbines needed for the same amount of electricity generated. Power cables needed consequently to be adapted to compensate for the increased load transport, with array cables rising from 33kV to 66kV and export cables rising from 132kV to 220kV. Every part of the supply chain went through a whole learning curve that brought us to where we are now. It also brought a lot of competition on the other hand. Contractors who weren’t able to catch up with the evolving technologies withdrew from the offshore renewable sector. Many new vessels have come in the offshore wind market that are for more capable than the first generation construction vessels which have led to lower cost of construction/installation. It is therefore important to have a strong and dedicated governments with clear policies and goals towards offshore wind to support investments made now and for future development in offshore wind that allows both developers and the associated supply chain to invest in their capabilities to support the continued expansion of offshore renewable energy zones. 

Europe is leading the transition to offshore wind energy, Denmark was the first country within Europe to do so. However the UK, Germany, Belgium, The Netherlands and France are now quite some knowledge centers. The UK has raised again their aspiration in generating capacity from offshore wind from 40GW to now generate 50GW of energy from offshore windfarms by 2030, I assume the UK will have further development aspiration’s offshore with their goal for net zero carbon emissions by 2050.  Most of the current commissioned offshore wind farms are fixed bottom foundations although floating windfarms are now at demonstrator phase and will move to utility scale production over the next decade.  Norway will most likely move towards floating in view of  their deeper water depths of the continental shelf. In Asia, Taiwan is the most mature market apart from China who are now world leaders in offshore wind generation capacity. With South Korea and Vietnam now showing emerging signs of moving to utility scale offshore windfarms and Australia in the early development stages of their first large offshore windfarm.  This coupled with the demand for high voltage interconnector cables that will provide submarine transmission systems between different geographical areas to distribute the generated power to the demand center’s means there is now a huge demand for submarine power cable supply. 

These transmission systems, whether renewable energy zone or interconnector submarine cables will be critical infrastructure systems that are key to removing reliance on hydrocarbon generating sources.  The reliability and associated integrity monitoring of submarine power cables will play a key role in maintaining the supply of green energy to the demand center’s.

How are subsea cables laid?

As for the laying of subsea cables, it is most important to have a vessel with good storage capacity for the cable. Many cable installation vessels nowadays also have rotating turn tables, ensuring that there is no torsion in the cable when it is being laid. All modern cable laying vessels are of incredible capacity and power. In the earlier stages of offshore wind farms development the farms were mostly built near shore. As the natural evolution of larger windfarms further offshore in deeper waters and the increased turbine generator capacity, the submarine power cables became longer and in general larger, which pushed cable laying vessels to adapt as well. 

Export cables, connecting the offshore substation with the beach, are longer and larger compared to infield cables, which connect the different wind turbines with the offshore substation. Export cables are normally laid and buried at the same time. The cable vessel itself is mobilized with a cable plough to simultaneously lay and bury the cable into the seabed, mostly between 1 and 3 meters deep. Infield cables are less long and are mostly surface laid and post lay buried. In general, 90% of the cable is buried since this protects the cable from external damage. However this also depends on the hardness of the seabed soil composition, if the seabed is too hard it will be a challenge to utilize a submarine cable trencher. An alternative in this case is to protect the cable through rock placement over the cable; however this can be significantly more expensive than cable burial. 

Interconnectors are high voltage transmission cables from country to country, they are mostly surface laid on the seabed and post lay buried. These cables tend to be HVDC  cables  with two conductor cables and in some cases include a fibre optic monitoring cable. These transmission systems are installed by bundling the cables together on the installation vessels before deployment to the seabed. As interconnectors increase in their route lengths, moving into deeper waters or perhaps off continental shelf areas the installation techniques will need to adapt and potentially move towards conventional single cable installation techniques.

What do you see as the biggest risks related to subsea cables?

To be honest, I think the risk for submarine cables were never well addressed. In the past, everyone thought that submarine cables were designed for the lifetime of a windfarm, which is in general 25 years. In the early development phase of offshore windfarms from a risk perspective submarine cables were considered low risk with low likelihood of failure.  However in my opinion this assumption was flawed and appears to have be borne out from the reality of cable failures experienced to date.  Since I have been installing cables, I have also been repairing cables. There is quite a misunderstanding about the risks involved with submarine cables. On the one hand we should understand that the cheapest way to make and lay a cable isn’t the most cost effective, on the other hand we need to understand we won’t be able to escape from third party damage or harsh/mobile seabeds. 

Currently some cable issues are being highlighted more. Last year for example Orsted came out with the news that they were dealing with failing cable protection systems, estimating the total impact to cost them around 350 million USD. This year they have updated this statement saying the impact will not be as high as expected. Another issue is that currently subsea cables are designed to be static, whereas the part which is protected by a CPS, this section of the submarine transmission system is dynamic as it rises from the seabed to the turbine foundation entry point in the water column and thus has a risk of movement from wave or tidal stream action which could lower the fatigue life of the submarine cable. It would be great if we could therefore focus more on subsea cable health monitoring. Whereas we see that offshore foundation topside health monitoring has been evolving, the same can’t be said for the part of the wind turbine below sea level.  

Cable protection starts right at the very design stage of a transmission system, what does the owner/operator want their cable to achieve? Followed by the design brief to the cable manufacturers to achieve the expectations of the cable owner/operator, including any inbuilt protection requirements.  The planned cable route requires thorough assessment and engineering to ensure the transmission route protects the cable as far as is reasonably practicable.  Once the design is frozen and the route engineered the cable requires manufacturing to the expected standards, with appropriate quality checks throughout the manufacturing process with associated acceptance tests.  The cable then requires to be transported to the worksite without compromise and installed along the agreed cable route using good installation practices, including any cable protection requirements through burial or other forms of external cable protection.  Once the transmission system is handed over to the owner/operator the operations and maintenance regime commences, within this period good practice asset integrity monitoring is key to ensure proactive asset management takes place rather than reactive management responding to a catastrophic failure once it has occurred.

What’s the failure rate of a subsea cable?

Historically insurers worked with a failure rate assumption that there may be 1 cable failure per 1000km per year. This doesn’t sound very high, however taken into account that in the UK there might be around 26000km of submarine power cables, this means we are talking about 26 cable repairs per year. A cable repair vessel may require around 3 months to repair a cable, so it could only take up 4 repairs a year potentially. To cover all the cable faults, this equates to the need of around 6 or 7 repair vessels a year.  In view of  the booming offshore wind market globally, all resources are quite high in demand with availability at short notice unlikely; so cables might be out of service for quite a while. I actually suspect the cable failure rate to be higher than 1 per 1000km, it could be around 1 per 750 km. Therefore by monitoring cables throughout their lifetime, potential failures can be detected upfront and any preventive repair measures can be planned, allowing for far more cost effective asset management. I believe truly this is the direction the industry needs to take.

So what makes good asset integrity management for submarine power cables?

Surely it’s the closest we can get to real time monitoring of the submarine transmission system that can capture data on relevant integrity issues for the submarine cable.  This data allows for predictive maintenance practices that can indicate potential failure times and allow remedial action to take place in a planned manner at an appropriate time of low transmission and cost effective availability of repair assets.  Marlinks are building a solid track record in providing distributed sensing techniques for submarine power cable integrity monitoring, providing data acquisition and interpretation services for submarine power cable owner/operators and their asset management teams.

Learn more about Marlinks.

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