Design, installation, and field experience with an overhead transmission dynamic line rating system

Dynamic line rating (DLR) systems for high voltage overhead transmission lines have been installed by three utilities over the past five years. These DLR systems utilize the Power Donut^TM to measure load and conductor temperature at several locations over the length of the circuit. The effective wind acting on the conductor at each site is determined in real-time by a dynamic heat balance and used to compute the normal, LTE and STE ratings each minute. The lowest ratings of all locations define the circuit´s ratings and are sent to SCADA as analog signals. This method is known as the conductor temperature model (CTM) as opposed to the weather model (WM) which calculates ratings using weather data only. These first DLR installations have also measured weather parameters at each ground station location to allow a comparison of the two methods. Data from the latest of these systems is presented and the behavior of the real time ratings are discussed