Low Wind Speed Heat Loss Analysis for DLR Applications

Dynamic line rating (DLR) is a technology that maximizes the capacity of the power system by dynamically adjusting the system capacity to the actual weather conditions. In DLR approaches, line capacity or ampacity is calculated using thermoelectric conductor models, which are highly sensitive to the effect of wind, especially at low wind speeds, which have the strongest effect on conductor temperature reduction. Due to its powerful cooling effect, wind speed plays an important role in determining conductor temperature. In this paper, experimental tests are conducted to analyze the thermal behavior of four transmission line conductors, i.e., two aluminum alloy conductors (AAAC), one aluminum conductor steel-reinforced conductor (ACSR), and one high-temperature, low-sag conductor (HTLS). The tests were performed in a laboratory environment under controlled temperature and wind conditions. International standards such as IEEE, Cigré and IEC propose formulations for both natural and forced convection, which are evaluated and compared in this paper using experimental laboratory data. The results show that while the proposed natural convection formulations found in the standards give very similar results, forced convection formulations can lead to significant differences in conductor temperature and ampacity prediction. Since forced convection plays an important role in determining the conductor temperature, the results presented in this paper are useful to better understand the effects of forced convection and to avoid miscalculations.