Unlocking thermal and ampacity headroom of medium-voltage cables: towards a component-aware distribution planning framework

This paper proposes a component-aware distribution network planning framework based on dynamic cable rating (DCR). The framework quantifies the thermal/ampacity headroom and capacity potential of MV cables, while explicitly considering the additional thermal ageing induced by increased loading. It enables distribution system operators (DSOs) to assess to what extent existing cables can be safely utilised to accommodate additional RES capacity, thereby alleviating congestion.

The framework is applied to several MV underground cables operated by a Dutch DSO and connected to either PV plants or wind turbines. Thermal and ampacity headroom is evaluated under four thermal limits: conductor temperature limits of 90 °C, 105 °C and 130 °C, as well as an outer sheath temperature limit of 45 °C. Although the 105 °C and 130 °C thermal limits are controversial, they are included to illustrate their impact on thermal ageing while acknowledging the added uncertainty. The methodology consists of three steps: 1) determination of load amplification factors up to the thermal limits, 2) normalisation of ampacity headroom relative to static ratings, 3) and quantification of additional thermal ageing using an Arrhenius-Miner model.

The results show that, under typical soil conditions, all investigated cables exhibit considerable ampacity headroom at the 90 °C thermal limit, with limited additional lifetime loss. PVconnected cables consistently provide higher ampacity headroom than wind-connected cables.

Sensitivity analysis on soil parameters indicates that headroom remains available even under unfavourable soil conditions. Raising the thermal limit to 105 °C and 130 °C further increases both ampacity headroom and capacity potential, but the associated thermal ageing increases sharply. When the 45 °C outer sheath exterior surface temperature limit is applied, windconnected cables show no ampacity headroom, whereas PV-connected cables retain a positive margin.

Overall, this study demonstrates the value of an integrated framework for MV distribution network planning. By combining DCR-based headroom estimation with explicit thermalageing assessment, the framework quantifies uprating potential and its associated risk to support planning decisions. This can increase cable utilisation, facilitate cost-effective RES integration, help alleviate grid congestion, and defer network reinforcement investments.