Lumped-parameter and finite element models of overhead power line conductors for dynamic thermal rating purposes

The steady-state approaches traditionally used to assess the capacity of overhead transmission power lines are being progressively replaced by procedures that consider the real and extremely variable weather conditions that are present along the path of the line under analysis (Dynamic Thermal Rating). Dynamic Thermal Rating (DTR) does not just estimate the temperature of the conductor in the different spans of the line, but also some mechanical quantities like their tension and sag, in order to appreciate the limitations imposed by the constraint of the minimum ground clearance. Modern DTR procedures need, therefore, proper mechanical models of the lines, in order to assess what happens both in normal and fault conditions. This paper proposes a comparison between a Finite Element Method (FEM) and a novel lumped-parameter model implemented through the Modelica language. Different realistic scenarios have been considered, like gusts of wind and the presence of ice. The outcomes of the two dynamic models have been compared to identify a trade-off between the accuracy of results and the computational time, as well as the dependency on the number of lumped masses used to model the line.