Subsea Cable Failures: What We Know and What We Don’t

Published 19 April 2021

By Charlotte Strang-Moran, ELECTRODE Project Lead and Electrical Engineer at ORE Catapult

“There are Known Knowns, and there are Known Unknowns”, as a well-known US Secretary of Defence once said. This is an excellent starting point for a discussion of subsea cable failures in the offshore wind sector, with emphasis on the Known Unknowns.

The biggest challenge we face is the lack of data. We do not have industry-wide trended data, so  researchers, manufacturers, operators, and developers only have their own experience to draw on. That is about to change with the launch of our ELECTRODE programme that  will provide the offshore wind sector’s first trended analysis of subsea cable failures, drawing anonymised data from across offshore wind sites and the supply chain.

ELECTRODE is a timely initiative. To meet the UK’s 75GW target by 2050, offshore wind sites will have to push further offshore to harness the strongest wind conditions. More powerful wind at the surface means harsher conditions below the waves too. That is why increasing the resilience of subsea cables and reducing failure rates is a priority for our sector and for myself and my colleagues in ORE Catapult’s ELECTRODE and High Voltage Laboratory teams.

Known Knowns

So, what do we know already? We know a lot about costs and consequences of subsea cable failures. The most commonly quoted estimate (although estimates vary) is that 75-80% of the industry’s insurance claims are related to cable failure. We know of individual cases that can cause losses of £10 million and more when lost output and repair costs are added together. One consequence of this bank of historical loss data has been a hardening insurance market for offshore wind.

We also know that there is no single pain point or culprit behind failures, and we know that environmental damage (accident, nature and acts of God) is responsible for only a minority of cases. That means that most cable failures are down to things that are under our control (and thus fixable): flaws and damage arising during manufacture, handling by transportation companies and faulty installation.

Known Unknowns

Failure Rates

While we know each cable failure is a costly business, we do not know how often cable failures actually occur. The data we gain from the ELECTRODE database will clear up a few known unknowns:

  • Where and when cable failures are likely to happen (annual failure rate per kilometre of cable, failure rates per component and mean time between failures use of new technologies in addressing failures)
  • Recurring causes of cable failures
  • Effectiveness of protection systems and management strategies

Seabed Mobility Standards and best practice

Seabed mobility refers to the action of waves, tides, mega ripples, sand waves and the wide variety of phenomena that can disturb a cable in the seabed. Best practice for studying seabed mobility is another grey area and one we intend to provide better information and guidance on risk management for industry.

Monitoring Best Practice

There is also a need to identify best practice when monitoring existing assets. Which technology is best suited to this task, how should it be implemented, and who defines what best practice is in terms of monitoring? We plan to develop a set of monitoring guidelines that will clear up some of the unknowns in this area.

Contact ELECTRODE and our research teams

As we kick-start our ELECTRODE project and continue our R&D into subsea cable failures, we are always looking for technologies, concepts and collaborators from across the supply chain.

For more information on how you can get involved, contact us at  We can also point you in the direction of our SME support programmes and funding streams for business and technology development.