Thermal Rating Modeling of Buried Inter-Turbine Array Cables Under Variable Sediment Conductivity

All buried cables generate heat during operation due to conductor and sheath losses. That heat must dissipate through surrounding sediment to the relatively stable deep-sea environment (~4°C). Unlike land-based cables, offshore sediments vary dramatically — from loose, saturated sands (good conductors) to stiff, desiccated clays (poor conductors) — and their thermal properties depend strongly on water content, density, and mineralogy. Ignoring this variability leads to either dangerous overheating or costly over-engineering.

Thermal rating modeling starts with solving the steady-state heat conduction equation ∇·(λ∇T) + q_gen = 0, where λ is position-dependent thermal conductivity and q_gen is volumetric heat generation. In practice, this is solved numerically using finite-element methods (FEM) or analytically via equivalent thermal circuit models (e.g., IEC 60287 series). Critical inputs include measured ρ_sed (not assumed), burial geometry, ambient seawater temperature profile, and tidal/current-induced sediment advection — the latter often neglected but significant in shallow, energetic environments (<30 m depth).

Advanced modeling incorporates transient effects: seasonal sediment temperature cycles, scour/fill events altering burial depth, and HVDC harmonic losses causing non-sinusoidal heating. Coupled hydro-thermal-mechanical (HTM) simulations are emerging for long-term lifetime prediction — tracking how repeated thermal cycling degrades sediment structure (e.g., clay cracking → increased λ) or accelerates corrosion under sheath defects. Machine learning surrogates trained on FEM datasets now enable real-time ampacity updates from DTS and CPTu feeds — moving beyond static ratings to adaptive thermal management.