State-of-the-art review of post-installation effects on subsea cable thermal properties for rating calculations

This paper consolidates existing evidence from onshore cable systems, offshore pipeline studies, industry research programmes, and in-service temperature measurements to demonstrate that installation-induced soil modification is both well-established and relevant for offshore wind applications. These findings indicate that conventional rating approaches may underestimate cable performance in certain geological settings, particularly where trenching or controlled backfill displaces thermally limiting soils. To enable the practical use of PIE in offshore cable design, the paper proposes a methodology based on an equivalent thermal resistivity (EQTR) approach. This method captures the influence of layered soils and installation-induced changes while remaining compatible with

IEC-based rating calculations. Benchmarking against numerical finite-element simulations confirms that this approach provides accurate results suitable for use in design practice.

Key implementation considerations are also addressed, including the behaviour of disturbed or backfilled soils, the role of trench geometry, and the management of uncertainties. A simplified and conservative trench representation is recommended to ensure robustness while still capturing the dominant thermal mechanisms. The paper demonstrates that PIE are most beneficial in high-resistivity environments, where installation can replace or redistribute soils that would otherwise limit ampacity, while benefits are smaller in more favourable sandy seabeds.

Overall, the results show that incorporating PIE into cable rating assessments can reduce unnecessary conservatism, improve ampacity estimates, and support more efficient utilisation of subsea cable assets. Continued research into mixed-soil behaviour, especially for jet-trenching, along with further validation through in-service monitoring, would support wider industry adoption and future integration into international cable-rating standards.