The subsea power cable market, here referring to array and wind export cables and interconnectors, is entering a period of expansion, driven primarily by offshore wind and electrification. However, this growth is shadowed by a significant and escalating problem: cable failures. With demand set to outpace repair capacity, market players face critical challenges in maintenance, protection, and resource allocation.
But what are some of the key factors contributing to the subsea cable failure trend and what are the potential solutions that will ensure the reliability of this vital infrastructure?
The number of active cables is increasing
The subsea power cable market is going through a period of significant growth, led primarily by the expansion of offshore wind energy. With a global target currently sitting at 183 GW by 2035, demand for both array and export cables will follow the same upward trajectory. The amount of active power cables alone is expected to increase 5.5x by 2040.
Furthermore, demand for longer interconnectors is rising with a move from country-to-country links to continent-spanning projects like X-Links which will connect the UK and Morocco and the AA Power Link between Singapore and Australia.
Most cable failures are located in Europe
European dominance in the number of cable failures is logical given it has the highest concentration of power cables globally at 93%. It is trailed by Asia, with just 4% and 3% in North America.
Globally, the 40,000 km of active export cables and interconnectors have seen around 170 failures since 2016 (detected using Spinergie’s algorithms). This is almost eight times less than the number of telecom failures (between 150-200 each year). However, it should also be noted that there are almost 1.4 million km of active subsea telecom cables.
The cause of cable failures are varied….
…But damage caused by vessel anchors and fishing gear is the most common cause (between 70-80% of all incidents according to the International Cable Protection Committee - ICPC). The remainder are due to manufacturing defects, misuse, or natural causes such as seafloor currents or sediment floors.
It is long power cables - including telecom, wind export, and interconnector - which are most at risk of anchor-related accidents. Smaller cables, like wind arrays, are typically concentrated in one area so are naturally better protected from anchors. However, they are still vulnerable due to the high number of connection interfaces with turbines and the substation. The main root cause is usually found at the base of the foundation due to failures in scour protection. In addition to manufacturing faults and natural hazards, inadequate design and installation damage can also be contributing factors.
The need to protect cables from failure is one of the most pressing needs facing the sector. Even though there are existing methods of protection, including cable burial, the use of mattresses and rock installations, they are not always suitable and, even when in place, they might not be enough to fully prevent damage.
There is one further notable reason for cable failures, one which has become more prevalent in recent months: the deliberate sabotage of subsea infrastructure. Several cases have been flagged as potential victims of this type of damage, most of them in the Baltic Sea, including, Balticconnector (a pipeline), EstLink 2 (a power cable), and C-Lion 1 (a telecom cable). However, these incidents are currently classed as suspicious, not certain, and, in some cases, investigations are ongoing.
Cable failures are only expected to increase
There are three main reasons that cable failures are set to increase in the coming years:
- Cable volume is expected to increase 5.5 times between now and 2040.
- Europe’s “ReArm Europe” plan is reflective of the current tense geopolitical context - there is greater potential for sabotage.
- The shipbuilding market is also poised for growth which will increase marine traffic and, in turn, the potential for anchor damage.
Spinergie currently forecasts that the number of cable failures is expected to increase 16-fold between now and 2036.
Prevention is better than cure
As mentioned earlier, there are some preventative measures to protect subsea power cables including enhanced cable protection design, mechanical protection (especially in high traffic areas), continuous surveillance and incorporating redundancy into the scope. All share a common goal: avoid damage before it happens.
Inevitably, there will need to be corrective measures and the key is to act fast. This means quickly mobilizing a repair vessel to address damages efficiently and restore operations as soon as possible.
The CLV fleet faces the most pressure from rising cable failures
Today, 60% of repairs are carried out by the same vessels that lay cables (CLVs). This includes, but is not limited to, fleets from Jan de Nul, Boskalis and Nexans.
Cable Laying Vessels (CLVs) are most commonly used because they already have all the necessary equipment and trained crews. They are best equipped for repairs on long sections which require a substantial load capacity and are likely to be in deeper waters.
The remaining 40% are handled by market players who focus on repairs rather than laying cables. On average, 50% of their usage over the past three years has been dedicated to cable repairs with the two main players being N Sea’s ‘Curo’ and Baltic Offshore’s ‘Pleijel’. These vessels are smaller than CLVs and barges, so they are not suited for all types of repairs.
There are other vessel options in the market
Spinergie has observed the mobilization of construction vessels with certain specifications, like ROV capability, a large deck area for storing a carousel, and DP2 capabilities.
AHTS vessels are also used to tow repair barges, especially in Asia for cable repairs in shallow waters. These vessels can be perfectly sufficient for repairs that only require lifting cable from the seabed and splicing.
Since the power cable market remains small in comparison to telecom, there is no dedicated repair fleet yet. Instead, repairs rely on an opportunistic and versatile fleet.
Despite these options, there is doubt the current fleet will cope with demand
Spinergie analysis indicates that O&M demand in vessel days is expected to increase 2.6 times between 2026 and 2036, growing from two full-time vessel equivalents to five. By 2036, this demand will reach a critical point with failure occurrences coming in line with what is currently observed in the telecom sector.
This leads to concerns over whether the existing fleet will be able to keep pace with demand, with it already under pressure from installation requirements. It is also unclear whether new players will enter the market.
According to Spinergie’s cable forecast, at least 12% of the total demand for export cables will remain unmet by 2030. Similar pressure is expected on the market for laying array cables. But while installations can be delayed due to pressure on the fleet, failures are unexpected and require urgent attention.
This could mean that, like the telecom market, the power cable sector could prioritize O&M over installation.
Read More: Offshore power cable demand is rising rapidly, but is the market equipped to cope with this boom?
To conclude, as demand for electrification projects, such as grid expansion and offshore wind cables rise, the CLV is under increasing pressure. Both cable installation and O&M sectors face challenges, with a bottleneck expected by 2026 for cable installation. However, there are
several solutions that could help ease the strain on the fleet:
- Enhanced security around critical infrastructures with military or coast guard support and stronger legal frameworks to reduce accidental and intentional failures.
- Shared maintenance contracts and repair fleets, similar to those seen in the telecom sector, to optimize repair resources and response times.
Further subsea cable insight can be found in our Subsea Cables Installation forecast. Find out how you can access the report here. You can access the replay of the webinar, including detailed case studies and a lively Q&A session, here.
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