A subsea cable failure may be discovered years after installation, but the circumstances that made it possible can originate much earlier. The cost of non-quality is not simply the cost of repair. It is the accumulated consequence of decisions, assumptions and controls that failed to prevent or adequately manage technical risk.
The offshore wind industry has demonstrated an extraordinary ability to develop and deliver increasingly complex infrastructure. Projects have grown in capacity, geographical scale and technical sophistication, supported by substantial advances in cable manufacture, marine construction and electrical engineering, yet subsea cable failures remain a persistent and expensive feature of the industry's operating experience.
This is not a new observation. The direct costs of cable repair, the consequences of prolonged generation outages and the demands placed on specialist marine resources are well understood. What is less readily established is whether the industry's commercial and engineering structures consistently provide the conditions necessary to prevent avoidable failures.
The issue is not simply whether we know how to design, manufacture and install submarine cables. The more uncomfortable question is why technically sophisticated organisations continue to experience failures associated with risks that are already understood.
The evidence: a costly and persistent exposure
The published evidence provides a compelling starting point, although the statistics require careful interpretation.
In 2023, the Offshore Renewable Energy Catapult reported that subsea cable failures accounted for approximately 75–80% of offshore wind insurance claims in the UK. It also noted that individual incidents can exceed £10 million in combined repair expenditure and lost generation, with repairs taking approximately two months on average. [1]
Allianz Commercial reported in February 2025 that subsea cable damage could account for approximately 70–80% of offshore wind losses by total claims value. [2]
These figures describe insurance experience, not the physical probability of an installed cable failing. They also reflect different populations and reporting periods and should not be regarded as directly equivalent as establishing reliable physical failure rates continue to present separate challenges.
The Carbon Trust's 2024 Floating Wind Joint Industry Programme review identified a reported failure-rate envelope for static offshore wind submarine cables of approximately 0.0019 to 0.0213 failures per kilometre per year, based on the studies and supporting data reviewed. [3]
This is a substantial range and as such should not be adopted as a universal project failure probability. Cable age, construction, environment, installation history and the definition of a reportable failure can materially affect the result.
Nevertheless, the available evidence demonstrates that submarine cable integrity remains a significant financial exposure whilst also revealing a weakness in the industry's ability to quantify that exposure consistently.
Publicly accessible data remains fragmented. Failure mechanisms are not always classified consistently, while commercial confidentiality and contractual sensitivities can restrict the sharing of operational experience.
Without a more comprehensive evidence base, it becomes difficult to establish whether improvements in design, manufacture and installation are producing measurable reductions in failure rates and for asset owners, insurers and investors, this uncertainty has consequences of its own.
The cost of non-quality is not the cost of repair
The financial impact of submarine cable failure is frequently presented in terms of repair costs and lost generation, both are important, but neither captures the complete economic consequence.
A failure can require investigation, fault localisation, engineering assessment, specialist vessel mobilisation, replacement materials, offshore repair, testing and recommissioning. Weather restrictions and availability of marine resources may extend an outage considerably.
Beyond the immediate intervention, further costs can arise through contractual disputes, insurance deductibles, uncovered losses, additional inspections, changes to operating arrangements and the reassessment of similar assets.
Where a common failure mechanism is suspected, the implications may extend across an entire wind farm or fleet, subsequently extending the cost of non-quality across the project lifecycle.
These include the consequences of inadequate prevention, incomplete verification, undetected defects and ineffective corrective action, as well as the cost of responding to failure once it occurs.
Not all these costs are avoidable, nor should every cable failure be attributed to poor engineering.
This distinction is important because expenditure decisions are often made at different stages, by different organisations, and from those that ultimately carry the consequences.
The party responsible for minimising an immediate project cost may not be the party that ultimately carries the cost of the resulting technical exposure.
When engineering becomes a percentage of contract value
Engineering is sometimes treated as a commercial allowance rather than a technical requirement.
During tender development and contract execution, engineering expenditure may be established as a percentage of contract value or constrained by a budget determined before the complexity of the work has been fully understood and resolved.
There are though, legitimate reasons to control engineering expenditure. Engineering resources are finite, unnecessary analysis creates cost, and repeated verification without a clear purpose adds little value.
The problem arises when the available commercial allowance becomes the determining factor in the engineering scope rather than the technical risks and uncertainties associated with the work. That reverses the proper relationship between engineering and project risk.
A design package may contain the required calculations. Procedures may have been reviewed and approved. Risk registers may be maintained, and contractual hold points formally released yet the project may still retain significant uncertainty at critical interfaces.
The relevant question is not whether the allocated engineering budget was consumed or whether every document was completed, it is whether the engineering undertaken was sufficient to substantiate the decisions on which the integrity of the asset depends.
This is particularly important where responsibilities are distributed between cable manufacturers, installation contractors, cable designers, specialist equipment suppliers, marine warranty surveyors and asset owners.
Each participant may fulfil its contractual obligations within a defined boundary while assumptions affecting the wider system remain inadequately reconciled.
A cable manufacturer may establish allowable mechanical limits against an agreed design basis. An installation contractor may demonstrate compliance with an approved installation analysis. A protection system may be independently qualified against specified loading conditions.
The engineering challenge lies in demonstrating that those assumptions, interfaces and conditions remain compatible in the completed system as a compliant component does not necessarily produce a reliable system.
The answer is not automatically to increase engineering hours, introduce additional review stages or commission progressively more detailed analysis, more engineering is not necessarily better engineering.
Poorly defined engineering can consume considerable resources without materially reducing uncertainty. Excessively conservative assumptions can produce unnecessary operational restrictions or costly interventions, while repeated reviews may provide an appearance of assurance without improving the underlying technical evidence.
The objective must be engineering sufficiency: an appropriate level of analysis, verification and independent challenge, directed towards the uncertainties that genuinely influence failure probability and consequence.
What matters is not simply how much engineering has been undertaken, it is what uncertainty that engineering has resolved, what decisions it has supported and what residual risk remains.
Standards establish expectations. Engineering must establish confidence.
Learning from decades of oil and gas development operations, the offshore wind sector now operates within an increasingly developed framework of technical standards and recommended practices.
DNV-ST-0359, updated in December 2025, establishes requirements for subsea power cable systems within offshore wind plants, including associated components and interfaces. [4]
DNV-RP-0360 provides lifecycle guidance for subsea power cables in shallow water, with particular emphasis on risk-based engineering and the reduction of risk to acceptable levels. [5]
IMCA M 264, published in 2023, provides a code of practice for offshore cable laying, addressing the cable-lay spread, vessel interfaces, installation methods, burial, trenching and associated operations. [6]
These documents represent substantial accumulated engineering knowledge and provide an important basis for technical assurance however; their existence does not eliminate project-specific uncertainty.
An installation analysis is only as representative as its inputs, assumptions and boundary conditions. Equipment qualification is only relevant to the extent that the actual operating conditions remain within the demonstrated envelope.
Likewise, acceptance against a contractual specification does not necessarily demonstrate that every credible failure mechanism has been adequately addressed.
The relationship between cable installation engineering and the integrity of the final installed system is not whether accepted analytical techniques exist for cable loading, lay configuration or touchdown behaviour.
It is whether the analysis is sufficiently representative of the cable construction, installation equipment, operating conditions and consequential activities, and whether deviations from that basis are recognised and controlled.
The same principle applies to cable protection systems, foundation interfaces, crossing arrangements, burial and subsequent remedial intervention.
These are not isolated design problems. They are system-level engineering challenges involving multiple organisations and stages of the asset lifecycle.
DNV's continuing Joint Industry Project on cable protection systems is instructive. Its September 2026 update identifies failure mechanisms, system responsibilities, interface management and global analysis methodology as areas of ongoing work, with new recommended guidance planned for 2027. [7]
The significance is not that earlier practice was necessarily inadequate, it is that engineering knowledge continues to develop, while installed assets and projects already under construction must be managed against the evidence available at the time.
Insurance: financial protection is not an engineering control
Insurance plays an indispensable role in the financing, construction and operation of offshore wind infrastructure.
It provides mechanisms through which specified financial consequences of unforeseen events can be transferred, subject to policy terms and conditions.
However, the availability of insurance should never be confused with the adequacy of engineering risk management as the two functions are fundamentally different.
Engineering seeks to understand, prevent and mitigate failure whilst insurance provides financial protection against defined losses when insured events occur.
The existence of an insurance policy does not reduce the physical probability of cable failure, and it does not restore lost generation or eliminate the operational disruption associated with a major repair campaign, a financially insured failure remains an engineering and operational event.
The distinction becomes particularly important when insurance is treated, explicitly or implicitly, as a safety net for technical uncertainty that could reasonably have been reduced before construction.
A project developer, contractor, asset owner and insurer may each carry different elements of the financial consequences associated with a failure. The allocation of these consequences through contracts and insurance does not necessarily mirror the allocation of responsibility for the primary engineering decisions.
There is no implication that insurance encourages poor engineering, or that contracting parties deliberately accept avoidable defects. It does, however, create circumstances in which technical and financial exposure can become separated.
The insurance industry is itself developing a more sophisticated understanding of offshore wind risks.
Allianz Commercial has highlighted the increasing technical complexity and cost of offshore renewable energy claims, including subsea cable damage and the dependence on specialist vessels and port facilities. [2]
Historical losses have contributed to more demanding scrutiny of technical risk. Nevertheless, insurance premiums do not follow a simple upward trajectory.
Reporting published by RPC in January 2026 identified softer conditions across parts of the renewable energy insurance market during 2025, with increased capacity, competition and more favourable terms. [8]
These developments should not be interpreted as evidence that the underlying technical risks have disappeared however; insurance pricing reflects market capacity, competition, claims experience, policy structure and wider commercial conditions, as well as project-specific exposure. A reduction in premium is not necessarily a reduction in technical risk.
Equally, a higher premium does not automatically indicate deteriorating engineering quality.
For developers and asset owners, the more valuable question is whether the underlying technical risk can be demonstrated to have been reduced, and whether that reduction is reflected appropriately in the project's financial exposure.
Insurance can transfer certain financial consequences of failure. It cannot transfer the engineering responsibility to prevent that failure.
Learning lessons, or simply recording them?
The offshore industry has accumulated extensive experience in failure investigation, root-cause analysis and lessons-learned processes and much of that experience has contributed to meaningful improvements in engineering practice.
Yet the recurrence of familiar failure mechanisms raises questions about the effectiveness of how that knowledge is understood and transferred.
An investigation may correctly identify a technical cause. Recommendations may be issued, procedures revised and the matter formally closed.
However, there is a considerable difference between recording a lesson and demonstrating that it has changed subsequent engineering and operational decisions.
Effective learning requires the investigation findings to influence the design basis, procurement specifications, installation engineering, equipment qualification, acceptance criteria and operating procedures of future projects.
What is often missed though is that it also requires an assessment of whether similar vulnerabilities may exist within assets already installed or under construction.
A particularly relevant example emerged from the Carbon Trust's Offshore Wind Accelerator programme.
In 2021, the Carbon Trust published recommendations addressing fibre-optic-related export cable failures. These followed an earlier UK review in which six of seven post-commissioning export cable failures were associated with optical-fibre issues.
The estimated combined repair and lost-generation cost was just under £23 million per incident.
The subsequent recommendations were expected to increase export cable costs by between zero and 0.5%, depending on the original design, without affecting installation costs. [9]
The comparison is significant, but it demonstrates how a relatively modest and targeted engineering intervention may be justified against the potential economic consequences of a known failure mechanism.
It does not establish that every historical failure would have been prevented by those measures, what it does demonstrate is the importance of connecting failure evidence to proportionate preventative action.
Industry initiatives such as ORE Catapult's ELECTRODE programme seek to address the limitations of available failure data through anonymised reporting of cable failures, downtime and the effectiveness of monitoring and repair methods. [1]
Such initiatives are important because no single contractor, developer or manufacturer necessarily possesses sufficient evidence to characterise the full range of industry experience.
The challenge is to translate that information into effective engineering practice while respecting legitimate commercial confidentiality.
Artificial intelligence and more sophisticated data analysis may assist with identifying recurring patterns, analysing technical records and making historical knowledge more accessible but the limitations must be recognised.
Incomplete, inconsistently classified or poorly understood data can generate misleading conclusions regardless of the sophistication of the analytical tools employed.
Automating the retrieval of lessons does not guarantee that the lessons are correct, relevant or effectively applied.
A lesson has not been learned merely because it has been documented. It has been learned when the next relevant decision is demonstrably different.
Understanding risk means understanding when not to intervene
Risk management should not be confused with the pursuit of eliminating every conceivable technical uncertainty.
In offshore construction and operations, attempting to remove one risk can introduce another. A cable protection arrangement or stabilisation system may exhibit a condition that differs from its original design expectation, that condition may justify further investigation, monitoring or physical intervention.
However, intervention itself can introduce mechanical loading, vessel interaction, seabed disturbance, additional handling or other operational exposures. The fact that a condition is imperfect does not automatically mean that immediate intervention represents the safest or most economical response.
Conversely, accepting a known deviation without establishing its potential failure mechanisms and consequences may leave an asset exposed to an avoidable loss and as such, the decision must be informed by credible evidence.
This requires consideration of the likelihood and consequence of the relevant failure mechanisms, the uncertainty in the available information, the effectiveness of existing controls and the risks introduced by potential remedial actions.
It also requires a realistic understanding of the limitations of probabilistic risk assessment. Quantitative techniques, including Monte Carlo simulation, can provide useful insight where the underlying distributions, dependencies and assumptions are supported by credible data.
However, additional mathematical complexity does not compensate for poor engineering inputs. A model may produce a precise result without providing an accurate representation of the actual risk.
The objective is not to demonstrate sophistication through increasingly elaborate analysis; it is to improve the quality of the decisions being made.
In some circumstances, that will justify additional engineering, testing or offshore work whilst in others, the most appropriate response may be continued operation under defined controls and monitoring arrangements.
Good engineering judgement is not measured by the amount of intervention recommended, but by the quality of the evidence supporting the decision.
The legacy we continue to build
One of the more difficult characteristics of submarine cable integrity is the potential separation in time between the creation of a defect and its ultimate manifestation.
An asset may complete installation, testing and commissioning while retaining a vulnerability that becomes evident only after prolonged operation.
Where this occurs, the organisations responsible for the original engineering and installation may no longer be contractually engaged.
Personnel may have moved on. Project records may be incomplete. Design assumptions and acceptance decisions may have become difficult to reconstruct.
The asset owner inherits not only the physical infrastructure, but also the consequences of the technical decisions made during its development, and this is a genuine legacy issue for any offshore development.
Assets installed under earlier specifications and assurance regimes must continue operating as industry understanding develops. Retrospectively applying every subsequent revision of a standard would not necessarily be appropriate or proportionate.
However, emerging knowledge should inform the assessment of existing assets, particularly where credible common-mode failure mechanisms or weaknesses in earlier design assumptions have been identified.
The challenge will become greater as offshore wind expands into more complex electrical systems and floating applications. Dynamic cable systems introduce different fatigue and qualification requirements, while the interfaces between cables, ancillary equipment and floating structures become increasingly important.
CIGRE Technical Brochure 862, published in 2022, provides recommendations for the mechanical testing of submarine cables for dynamic applications. [10]
The Carbon Trust's 2024 review also identified important limitations in the available dynamic cable failure data and the maturity of supporting qualification standards. [3]
These are areas where engineering knowledge is still developing and the lessons of static cable systems remain relevant, but they cannot simply be transferred without accounting for the different loading conditions and operating environments.
There is an uncomfortable possibility that the industry may be creating new legacy risks at the same time as it works to resolve earlier ones.
The response should not be to resist technological progress, it should be to ensure that engineering assurance, qualification and the management of uncertainty develop alongside it.
From engineering judgement to investment confidence
Offshore wind projects increasingly depend on the confidence of organisations whose principal responsibilities may lie outside day-to-day engineering.
Investors require confidence in the reliability and financial performance of assets, lenders need to understand the implications of technical uncertainty for availability, cash flow and debt servicing.
Insurers must understand the exposure being transferred and the effectiveness of measures intended to prevent losses and developers and contractors must make decisions within demanding commercial and programme constraints.
These interests remain closely connected. A technical decision affecting cable integrity may influence the operating performance of the asset for decades.
The challenge is therefore to translate engineering uncertainty into commercially meaningful information without reducing complex technical issues to misleadingly simple risk scores and this is where independent technical judgement has value.
It can challenge whether the engineering basis is sufficient, whether interfaces have been adequately addressed, whether assumptions remain valid and whether proposed mitigation measures are proportionate to the exposure.
It must also be prepared to conclude that further expenditure is unnecessary where the available evidence supports that position.
The objective is not to introduce another layer of approval or to transfer responsibility away from those delivering the work, it is to improve confidence in the decisions on which the technical and financial performance of the asset depends.
A different measure of quality
Offshore wind has achieved substantial reductions in cost and considerable improvements in delivery capability, and those achievements should not be discounted.
However, the continuing economic consequences of submarine cable failures suggest that further progress must be measured by more than installation efficiency, initial capital expenditure and programme completion. There is a need to consider the entire lifecycle cost of technical decisions.
That means recognising the value of engineering where it demonstrably reduces exposure, challenging engineering expenditure where it does not, and understanding the consequences of technical uncertainty before they are inherited by the operating asset.
It means ensuring that contractual responsibilities do not obscure system-level risks and that lessons learned are reflected in subsequent decisions rather than retained principally as historical records.
It also means recognising insurance for what it is: an essential mechanism for managing defined financial losses, not a substitute for sound engineering.
The cost of non-quality is not simply what we spend when something goes wrong. It is the economic consequence of what we failed to understand, challenge or control when we had the opportunity.
The objective should not be to become progressively better at repairing predictable failures, it should be to become demonstrably better at preventing them.
At Odyssey Marine Consultants, our focus is on connecting engineering judgement with the commercial consequences of technical risk — helping developers, contractors, asset owners and capital providers understand exposure, challenge assumptions and identify proportionate responses before uncertainty becomes an expensive reality.
Capital deserves clarity.
References
[1] Offshore Renewable Energy Catapult (2023). ELECTRODE – Electrical Cable Failure and Reliability Trending for Operational Developments. Published 4 May 2023.
https://ore.catapult.org.uk/resource-hub/projects/electrode
[2] Allianz Commercial (2025). Claims activity in the age of greening. Global Risk Dialogue, February 2025.
https://commercial.allianz.com/news-and-insights/expert-risk-articles/global-risk-dialogue-2025-net-zero-transition-claims.html
[3] Carbon Trust (2024). Floating Wind Joint Industry Programme, Phase V Summary Report. March 2024. Section 6, Dynamic Cable Failure Rates and Standards.
https://www.carbontrust.com/sites/default/files/2024-03/Collated-Summary-Report.pdf
[4] DNV (2025). DNV-ST-0359: Subsea power cables for wind power plants. December 2025 edition.
https://www.dnv.com/energy/standards-guidelines/dnv-st-0359-subsea-power-cables-for-wind-power-plants/
[5] DNV (2016; amended 2021). DNV-RP-0360: Subsea power cables in shallow water.
https://www.dnv.com/energy/standards-guidelines/dnv-rp-0360-subsea-power-cables-in-shallow-water/
[6] International Marine Contractors Association (2023). IMCA M 264: Code of Practice for Offshore Cable Laying in the Renewable Energy Industry. Revision 0.1, November 2023.
https://www.imca-int.com/resources/technical-library/document/3d5bc45a-c55b-ee11-8def-6045bdd2c3b2/
[7] DNV (2026). Qualification and Design Requirements for Cable Protection Systems. Joint Industry Project, September 2026 status update.
https://www.dnv.com/group/joint-industry-projects/qualification-and-design-requirements-for-cable-protection-systems/
[8] RPC (2026). Annual Insurance Review 2026: Energy and Power. Published 21 January 2026.
https://www.rpclegal.com/thinking/insurance-reviews/annual-insurance-review-2026/energy-and-power/
[9] Carbon Trust (2021). Offshore Wind Accelerator publishes new design recommendations to prevent export cable failure. Published 11 February 2021.
https://www.carbontrust.com/news-and-insights/news/offshore-wind-accelerator-publishes-new-design-recommendations-to-prevent-export-cable-failure
[10] CIGRE (2022). Technical Brochure 862: Recommendations for Mechanical Testing of Submarine Cables for Dynamic Applications. Working Group B1.63.
https://www.e-cigre.org/publications/detail/862-recommendations-for-mechanical-testing-of-submarine-cables-for-dynamic-applications.html