the cable breaks, the

wind farm goes dark

Problem statement

Submarine power cables are the critical link between offshore wind turbines and the onshore grid, and cable failures are the largest source of offshore wind insurance losses: GCube's "Uncharted Waters" claims report found subsea cables accounted for 30% of claims incurred and over 50% of total claims spend across 2010–2020, and IMCA reports insurers attributing between 50% and 70–80% of their offshore wind claims to subsea cable damage. Locating a fault in a buried submarine cable requires shutting down the affected circuit (losing tens to hundreds of MW of generation), deploying specialized cable-laying vessels (typical day rate around £150,000; BVG Associates), and excavating the cable from the seabed for repair. Fault location from the cable terminations (e.g., time-domain reflectometry) is coarse over long buried circuits, so extensive seabed survey is needed to find the actual damage point. Average downtime is around 40 days for an inter-array cable repair and 60 days for an export cable repair — including vessel mobilization and weather windows — with export cable damage costing $10–30 million per incident (University of Strathclyde figures cited by IMCA).

Why this matters

Global offshore wind capacity reached 83 GW by the end of 2024, and GWEC forecasts about 350 GW of additions over 2025–2034 (441 GW total by 2034). Installed offshore wind cable has grown six-fold from 9,000 km (2015) to 55,500 km (2025), with a further ~117,640 km forecast for 2026–2040 (TGS 4C). The average power cable failure rate is approximately 0.003 failures per km per year (University of Strathclyde study cited by IMCA) — low by onshore standards but devastating at offshore repair costs. Damage incurred during installation contributed to 46% of all power cable failures (ORE Catapult, cited by IMCA), and 44% of cable claims spend traces to contractor error in transit and cable laying (GCube). Faster, cheaper cable fault detection and repair would significantly reduce the levelized cost of offshore wind energy.

What’s been tried and why it hasn’t worked

TDR and frequency-domain reflectometry (FDR) provide fault location from cable terminations but with accuracy limited by cable impedance variations, joints, and branching points. Distributed temperature sensing (DTS) using fiber optic cables co-installed with power cables can detect hotspots indicative of insulation degradation, but most existing cables lack fiber optic elements. Partial discharge monitoring can detect incipient insulation faults but is unreliable over the long cable runs typical of modern offshore wind export circuits due to signal attenuation. ROV-based visual inspection can find external damage (anchor strikes, abrasion) but cannot detect internal insulation degradation. The fundamental challenge is that the cable is buried in the seabed, in an electrically noisy marine environment, and the failure modes (water treeing, mechanical fatigue, thermal cycling) develop internally and invisibly over years.

What would unlock progress

Embedded distributed sensing (acoustic, thermal, strain) integrated into cable design at manufacture rather than retrofitted. Real-time cable health monitoring systems that can detect degradation years before failure, enabling preventive repair during planned maintenance. Improved fault-location accuracy would shorten repairs by cutting the seabed search phase. Novel cable designs with modular repair sections or redundant conductors could reduce repair scope. On the vessel side, faster cable repair techniques that don't require full cable recovery to the surface would dramatically reduce repair duration and weather sensitivity.

Entry points for student teams

A team could design a cable health monitoring system concept, specifying sensor types, data processing architecture, and degradation detection algorithms for a representative offshore wind cable. Test data from cable manufacturers' accelerated aging tests (some published in CIGRE reports) provides a starting point. Alternatively, a team could model fault location accuracy improvement using distributed acoustic sensing (DAS) fiber integrated into cable design, simulating signal propagation and detection sensitivity.