Large Swing Behavior of Overhead Transmission Lines under Rain-Load Conditions

In recent years, flashover accidents caused by large swings of overhead conductors that frequently occurred under rain-wind condition, greatly jeopardized the normal operation of power transmission systems. However, the large swing mechanism of overhead conductor under the simultaneous occurrence of rain and wind is not clear yet. Thus, a unified model is proposed with derived stability criterion to analyze the large swing of the overhead conductor. The analytical model is solved by finite element method with the aerodynamic coefficients obtained from simulated rain-wind tests, taking into account the effect of wind velocities, upper rivulet motion, rainfall rates, and rain loads on the large swings of overhead transmission lines. The results show that the proposed model can capture main features of the large swing of overhead conductor, this swing being probably due to the upper rivulet’s motion, by which negative aerodynamic damping occurs at a certain range of wind velocity (10 m/s). Furthermore, the peak swing amplitude of the overhead conductors under rain-wind condition is larger than that under wind only, and the rain loads cannot be neglected.