Enhanced Heat Transfer Effect And Fatigue Life Analysis Of Overhead Conductor Under Aeolian Vibration

During the normal operation of High-voltage overhead transmission lines,there is always an interaction between ambient temperature and line current carrying capacity,which is often coupled with wind-induced vibration of transmission lines.In the wind-induced vibration of transmission lines,the probability of occurrence of aeolian vibration is the greatest and the duration is the longest.It can be considered that aeolian vibration is the normal working state of transmission lines.However,long-term aeolian vibration can cause fatigue strand breakage of conductors and damage of tower components,so aeolian vibration has always been considered as a harmful phenomenon.In fact,when considering the essential properties of overhead conductors,moderate wind-induced vibration(e.g.aeolian vibration)can enhance the convective heat transfer capacity of conductors,and thus can improve the steady ampacity of conductors.However,there are few studies on the beneficial effects of aeolian vibration on overhead conductors.Therefore,it is important to further study the effect of aeolian vibration on overhead conductors from the perspective of favorable and unfavorable effects.While making full use of the enhanced heat transfer effect of aeolian vibration to improve the current carrying capacity of conductors,it is also important to select appropriate control intervals for vibration reduction and to evaluate the fatigue life of conductors,which is of great theoretical significance and engineering guiding value for a more comprehensive understanding of the aeolian vibration effect of overhead conductors and making reasonable maintenance decisions.Based on the above background,this paper takes the commonly used LGJ400/50 steel-cored aluminium strand as an example.a fluid-solid coupling model for the analysis of overhead transmission lines under aeolian vibration is established The aerodynamic and heat transfer characteristics of single conductor and split conductor under aeolian vibration are studied by numerical method and heat balance theory.The beneficial effects of aeolian vibration on the enhancement of heat transfer and current carrying capacity of overhead conductors are analyzed.The amplitude range of the aeolian vibration is determined,which is most conducive to raising the carrying capacity of the conductor.On these basis,the vibration strength and fatigue life of overhead conductors in the above optimal amplitude range are analyzed.The main research contents and conclusions are as follows:(1)The aeolian vibration characteristics and temperature field of fixed single conductor and two-degree-of-freedom order conductor with different wind speed,different carrying capacity and different ambient temperature are analyzed by using overlapping grid technique under different vibration conditions.The results show that the aeolian vibration can effectively enhance the heat transfer capacity of conductor and reduce its temperature,the maximum heat transfer effect is achieved in the lock-in region,in which the temperature of the conductor can decrease the most.(2)The vibration characteristics and temperature field of the fixed split conductor and the vibrating split conductor under different spacing are simulated and analyzed under the three basic split arrangements of series,juxtaposition and stagger,and the wind vibration is used to simulate and analyze the vibration characteristics and temperature field of the split conductor under different spacing.The results demonstrate that when the split conductor is used,the vibration mode of the conductor in the wake becomes more complex and has a wider vibration range,and its vibration characteristics and temperature field are greatly affected by the upstream conductor.The change trend of the average temperature of the conductor is the same as that of the transverse amplitude.(3)Quantitative analysis of the heat transfer characteristics of conductors under different amplitudes is carried out by means of amplitude priori generation,and verified by single conductor heat transfer under the same conditions.The range of the vibration amplitude of the breeze which is beneficial to heat dissipation is found to be 0.1D~0.6D.The wind energy input power of the conductor is fitted.(4)According to the amplitude prior method,the wind energy input power of the conductor is fitted,and the parameters affecting the vibration intensity of the conductor(flexural stiffness,tension,amplitude,average temperature fixing and real-time variation of the conductor)are analyzed based on the principle of energy balance.The fatigue life of transmission lines with different bending stiffness,tension,vibration amplitude of breeze,fixed average conductor temperature and real-time variation is analyzed.Considering the influence of heat dissipation effect and service life of conductor,better heat dissipation effect can be obtained when the amplitude is controlled less than 0.4D,and the conductor has a better service life.