Wind, Temperature, and Solar Contributions to Dynamic Line Rating: A Sobol Analysis from Span to Corridor Scale

As renewable penetration and demand rise, many transmission corridors operate near conservative static ratings that assume high ambient temperature, full sun, and low wind. Dynamic line rating (DLR) can unlock headroom by adjusting allowable current (ampacity) so conductor temperature remains below its rating. We quantify the relative importance of weather drivers using Sobol variance decomposition of IEEE‑738 ampacity with respect to three input groups: wind (speed and direction), ambient temperature, and solar irradiance, for (i) a single span and (ii) contiguous line segments under summer conditions. Single‑span analysis uses Environment and Climate Change Canada station data; multi‑segment analysis uses HRDPS model fields. For a representative span, wind dominates ampacity variability across conductor temperature ratings, explaining ~60% of the first‑order variance at 49 °C and ~90% at 95 °C, while temperature and solar contributions decline monotonically as the rating increases. A model‑based replication with HRDPS reproduces these patterns, with slightly lower wind and higher temperature indices, consistent with smoothed model variability.When aggregating contiguous segments by the minimum ampacity across spans, wind’s contribution decreases with line length due to low spatial coherence: beyond ~20 km at low temperature ratings, the contribution of temperature and solar exceed wind's; for >100 km, wind’s share falls below 20%, and both mean ampacity and variance decline with length because of recurring locally calm spans. Operationally, these results support targeted wind sensing on short or high‑temperature corridors, while recognizing that ambient temperature (available without new sensors) becomes the primary driver for long, low‑rating lines.