| Overhead power transmission lines cross mountains,valleys and other environments to transmit electricity to thousands of households.As an important part of transmission lines,transmission wires are extremely vulnerable to ice,snow and strong winds.Especially after icing,they are very prone to galloping,resulting in line faults and power accidents.In practice,steel-cored aluminum stranded wires are mostly used for transmission wires,whose cross sections have obvious twisted features,namely non smooth circular ones.However,most studies on aerodynamic and galloping characteristics of ice-covered transmission wires basically consider the wires as circular ones,and the characteristics of non smooth circular twisted sections are not considered enough.At the same time,the galloping of iced transmission wires is a two-way fluid structure coupling phenomenon,and the analysis of the influence of conductor vibration on the flow field is insufficient in most studies.In addition,the fluid-structure interaction of ice-covered transmission wires is mainly based on the analysis of uniform wind field,and the influence of wind pulsation is seldom considered.Based on the above background,FLUENT software is used in this paper to analyze the aerodynamic and galloping characteristics of ice-covered transmission wires,taking JL/GlA-400-35 steel cored aluminum stranded wire as an example.The main contents and conclusions are as follows:(1)Using overlapping grid technology and hybrid grid,the models of smooth circular and non smooth circular cross-section iced conductors are established.The differences of aerodynamic characteristics and vortex shedding between the two cross-section conductors under different wind speed,different icing thickness,different icing shape and different conductor diameter are analyzed and compared.The results show that there are great differences in aerodynamic and vortex shedding diagrams between the two cross-section iced conductor models,and the maximum relative error of aerodynamic coefficient can reach-1.75.Therefore,the influence of conductor stranding on its aerodynamic characteristics should be considered in the refined wind resistant design of iced transmission line system.(2)Using the non smooth circular twisted section iced conductor model and the secondary development function of FLUENT software,the unidirectional and bidirectional fluid structure coupling analysis of single conductor is carried out,and the effects of different conductor vibration directions on conductor aerodynamic force,vortex shedding and galloping displacement are deeply analyzed.The results show that the aerodynamic force of the conductor fluctuates greatly under the two-way fluid structure coupling,and the fluctuation is more intense with the increase of wind speed.The flow direction vibration increases the transverse wind amplitude of the wire by 24%.When the Angle of attack is between 65° and 115°,it is more likely to produce downwind movement,and its maximum displacement can reach 7.5 times of the transverse wind direction.Torsional vibration can change the galloping shape of the conductor and change it from transverse and downwind to torsional galloping.(3)The difference of aerodynamic characteristics of iced split conductor under unidirectional and bidirectional fluid structure coupling is analyzed.At the same time,the aerodynamic and galloping characteristics of split conductor under different conductor vibration considering bidirectional fluid structure coupling are analyzed.The results show that the downstream conductor is more prone to cross wind galloping than the upstream conductor,and is more vulnerable to different forms of conductor vibration.The aerodynamic and galloping characteristics of the downstream conductor are affected by the wake of the upstream conductor,which can vary according to the different vibration directions of the conductor.It can be seen that considering the conductor vibration,it has a great impact on the aerodynamic and galloping characteristics of the split conductor.(4)Using the profile input mode,the two-way fluid structure coupling analysis of iced conductor under non-uniform wind field is further carried out,and compared with the aerodynamic and galloping characteristics of iced conductor under uniform wind field.The research shows that the aerodynamic coefficient and trajectory of conductor under non-uniform wind field can fluctuate greatly with the change of wind speed,and can become more violent and unstable.Therefore,it is necessary to consider the influence of non-uniform wind field on the aerodynamic force and galloping characteristics of iced transmission conductor under two-way fluid structure coupling. |
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