Enhancing Subsea Cable Reliability: Japanese Specialized Vessels Target Installation Risks, Not Just Repair Times

Subsea cables remain a critical vulnerability in offshore wind farms, responsible for 70-83% of insurance claims and significant financial losses [1]. Industry data highlight that installation damage accounts for up to 46% of failures, with nine out of ten cable-related insurance claims linked to laying processes [2]. Additional causes include manufacturing defects (31%), design issues (15%), and external aggression (8%), while repair downtimes—often cited as Mean Time to Repair (MTTR)—average 40-60 days for inter-array and export cables, exacerbating revenue losses [3].

The question arises whether innovations primarily advance prevention or merely facilitate faster repairs. Recent developments emphasize the former: Mitsui O.S.K. Lines (MOL) has obtained Approval in Principle from ClassNK for dedicated cable jointing and burial vessels, designed in collaboration with Sumitomo Electric, Furukawa Electric, and NYK Line under a NEDO-funded project [4]. These vessels enable precise offshore jointing of cable sections and deeper, more effective burial using advanced ROV operations, directly mitigating mechanical stresses and exposure risks during installation.

By specializing in high-precision jointing and burial, these vessels address root causes like improper handling and insufficient protection, rather than solely enabling quicker post-failure interventions. Improved installation quality reduces failure incidence, complementing efforts to manage MTTR through vessel availability.

As offshore wind scales with HVDC for distant sites, such preventive technologies could substantially lower overall failure rates and associated costs, fostering greater grid resilience.

In the concluding outlook, widespread adoption of specialized installation vessels may markedly decrease cable failures in future projects, supporting ambitious renewable targets.

[1] DNV - 80% of insurance claims in offshore wind are related to subsea cable failures [2] IMCA - Unravelling subsea cable failure in offshore wind [3] ORE Catapult - Subsea Cable Failures: What We Know and What We Don’t [4] Offshore Wind - Japanese Designs of Cable Jointing and Burial Vessels Get Green Light