Investigation and analysis of dynamic line rating in power systems by analytical, numerical and experimental methods

In light of the increasing global electricity demand and the operational challenges posed by aging transmission infrastructure, enhancing the capacity of existing transmission lines without extensive physical expansion has become a strategic priority. Accurately predicting the current-carrying capacity of conductors is of critical importance, and Dynamic Line Rating (DLR) systems have emerged as an effective solution. International standards such as IEEE 738 and CIGRÉ TB 601 provide structured and reliable frameworks for capacity estimation. This study aims to evaluate the performance of transmission conductors under various operating conditions, compare the predictive capabilities of the IEEE 738 and CIGRÉ TB 601 standards, and investigate the thermal behavior of single and bundled conductors within the DLR framework. The primary objective is to develop a more precise, flexible, and reliable methodology for assessing transmission line capacity. A combined approach integrating analytical, numerical, and experimental methods was adopted. COMSOL Multiphysics and the Finite Element Method (FEM) were employed to simulate the thermal and electrical behavior of conductors under varying environmental factors, different geometric configurations, and bundling arrangements. The simulations accounted for time-varying conditions such as wind speed and direction to capture realistic thermal responses. Additionally, comparative analyses between IEEE 738 and CIGRÉ TB 601 focused on key thermal parameters, including convective cooling, solar heating, and conductor emissivity. In the experimental study, the thermal behavior of single and double-bundled conductors under wind and environmental conditions was examined. Results indicated that windward surfaces experienced more effective convective cooling, whereas leeward surfaces were partially shielded and exhibited higher temperatures. In single-conductor experiments, the average surface temperature was measured as 49.71 °C and compared with simulation and analytical predictions (IEEE 738, CIGRÉ TB 601), with IEEE 738 providing the closest estimate. For double-bundled conductors, the protective effect of the windward conductor resulted in a leeward conductor surface temperature of 52.08 °C. These findings highlight that the unequal distribution of surface temperatures arises from local factors such as wind direction, turbulence, and conductor positioning, emphasizing the importance of considering these effects in assessing conductor thermal performance. When combining simulation and experimental results, the study demonstrates that the DLR approach yields conductor current-carrying capacities approximately 10–35% higher than traditional Static Line Rating (SLR) methods and illustrates the benefits of using real-time environmental data. In the DLR prediction study, meteorological data were employed to estimate transmission line dynamic current-carrying capacity using CNN and LSTM models; wind speed emerged as the most significant factor, and the models successfully captured the fundamental trends while effectively filtering short-term fluctuations. COMSOL-based simulations of bundled conductors showed that, due to turbulence effects and reduced convective cooling, downstream conductors consistently reached temperatures 3–5% higher than upstream conductors. This thermal difference underscores the importance of basing DLR calculations in bundled conductor configurations on the conductor experiencing the highest thermal stress to ensure accurate and reliable capacity assessment. Furthermore, the comparative evaluation of IEEE 738 and CIGRÉ TB 601 highlights the need for location-specific adjustments when applying these frameworks under dynamic operating conditions.