The Diligence Gap
Original design assumptions cover an asset's worst probable operating conditions — not what it actually experienced. At end of OEM design life, that gap becomes the central question in every repowering or life-extension decision, and most operators have no measured loading history to answer it. The default is conservative assumptions, applied uniformly across a fleet regardless of how any individual asset actually performed.
The regulatory ground is shifting under this too. IEC 61400-6 Amendment 1 (2025) moves tower and foundation fatigue assessment from design-based safety toward condition-based compliance, and DNV-ST-0126 explicitly identifies structural health monitoring data as a basis for remaining-useful-life determination. Without a baseline, the standards default to the conservative case — the one that shortens an asset's usable life on paper, whether or not it happened in practice.
SCADA captures tower data, but at 1 Hz it can't see beyond Mode 1 lock-in. Mode 2 and Mode 3 VIV events carry higher fatigue loads and are invisible to it entirely — which means the loading history most fleets already have isn't sufficient to support a life-extension case on its own.