Continuous Monitoring of Transmission Lines Sag through Angular Measurements Performed with Wireless Sensors

High voltage transmission lines are crucial infrastructure that are demanded to supply an increasing request of electric energy. In the design and operations stages, sag represents a key parameter which must respect specific constraints. Therefore, sag continuous monitoring is becoming essential to guarantee the correct functioning of the line and to optimize the current flow. Different solutions have been proposed in literature, but they are still lacking efficiency and reliability to be used during operations. In this work, a simple and efficient method, based on conductor parabolic approximation, is developed and used to compute the sag through the measurement of the conductor slope in proximity of the span extremities. The angular measurements are obtained using wireless sensors equipped with MEMS accelerometers developed by authors and employed for HVTL conductor vibration monitoring. The proposed method and its implementation in the monitoring system was tested in a laboratory environment on a real conductor. The values of sag at different tensile loads have been obtained and compared to the measured ones, with satisfactory results according to the accelerometer resolution. The solution developed therefore represents a complete and innovative tool to be adopted in the field to monitor, in real time, both the sag and the level of vibration due to the wind action, allowing to increase the performance reliability of HVTL.