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Abstract--With the large increase of distributed renewable electric energy generation, the need for more transmission capacity is obvious. As restrictions practically prevent building new overhead lines, options to increase transmission capacities of existing lines are inevitable. The transmission capacity of overhead transmission lines itself is often constrained by temperature limitations of the conductors. One strategy connected with smart energy transmission is to calculate present and future transmission capacities of the lines based on actual weather conditions and forecasts, rather than relying on a static and conservative fixed value. By this, an increased transmission capacity can be enabled. To do so, models to calculate thermal ratings have to be refined and improved, especially in the range of conductor temperatures close to their limits. In this temperature range, measurement data for assessing the accuracy of existing calculation methods is still scarce. The knowledge of the accuracy of the thermal rating calculation methods is vital as otherwise lifetime specifications of the conductors may be at risk. The paper explores the potential of dynamic thermal rating of overhead lines starting with state-of-the-art calculation formulas. The shortcomings of these formulas are discussed. One is the assumption of homogeneous temperature distribution within the conductors. The differential equation for the heat transfer in a cylindrical overhead line conductor is solved taking into account both the skin-effect on the current distribution and different heat transfer conditions. These calculations reveal relevant radial temperature gradients, underlining the importance of more elaborate and reliable thermal modeling of the conductors. Further, planned setups to perform laboratory-experiments are introduced. In particular, an overview of available temperature measurement systems and sensors being under evaluation for the upcoming laboratory and field measurements are presented. Index Terms--all aluminum alloy conductor (AAAC), distributed temperature sensing (DTS), dynamic thermal rating, power system management, real-time rating, smart transmission, transfer capacity, transmission lines. I