Experimental Validation of Adaptive Models for Dynamic Rating of Power Cables with Joints

The need for enhancing the grid flexibility is pushing system operators to revise the criteria adopted for determining the power component thermal ratings, which are traditionally based on static and conservative assumptions. The evolution toward a dynamic approach for thermal rating assessment is expected to hold significant benefits if applied to power cables, which often are the critical component limiting the load capability of the overall grid. Dynamic rating of power cables requires the deployment of accurate thermal models aimed at reliably predicting the transient evolution of the hot-spot conductor temperature, once knowing the load current and the environmental variables along the line route. This dynamic computation is often complicated by the presence of cable joints, which could influence cable heating to a considerable extent, introducing potential hot-spots. To solve this problem, in this paper adaptive modelling techniques are employed in the task of dynamically computing the thermal ratings of medium voltage cables in the presence of joints. The main idea is to model the joint heating by an equivalent thermal network, whose parameters are inferred from easily measured data by an indirect estimation algorithm. This calibrated thermal model is then deployed in the task of periodically computing the corresponding dynamic load capability curve, which considers the thermal inertia and the actual thermal state of the power cable. Detailed experimental results obtained on the laboratory test-bed of RSE (Ricerca sul Sistema Energetico) are presented and discussed in order to assess the benefits of the proposed computing approach.