Investigation on aerodynamic instability of high-voltage transmission lines under rain-wind condition

Abstract

Under rain-wind conditions, rain-wind induced aerodynamic instability phenomenon often occurs on high-voltage transmission lines. Like the effects of any other oscillations, this kind of vibration intensifies the fatigue of high-voltage conductors, especially on line supports or clamps. The presence of raindrops and wind associated with electric field maybe the main cause of this phenomenon. On rainy days, raindrops hit the transmission line and suspends to the high-voltage conductor. The suspended raindrops form upper rivulet and lower rivulet and take an elliptical arch shape along the surface of the high-voltage conductor by action of the wind, if rainfall is sufficient. Moreover, the rivulets are enlarged as a cone shape with the electric field of high-voltage conductor. The upper rivulet’s effect on the original cross-section formation of the high-voltage conductor and its movement are likely to be the cause of aerodynamic instability. The objective of this paper is to validate a two-dimensional model to investigate the effects of different parameters (electric field strength, wind velocity, frequency and damping ratio of the dynamic system) on aerodynamic stability of the conductor. The Lyapunov stability theory is applied to the model to derive the criterion for the instable angle of the rivulet. Moreover, an experimental conductor model with a moveable artificial upper rivulet is set-up and tested in a wind tunnel. The theoretical results are in good agreement with the experimental data. The model enable better comprehension of the rain-wind induced aerodynamic instability on the conductor.