The Study Of Aerodynamic Characteristics And Galloping Of Ice-coated Transmission Line

Galloping is one type of flow-induced vibration under the condition of non-circularcross section. Galloping of ice-coated transmission conductors is a high-amplitude andlow-frequency self-excited vibration. The large displacements induced by the phenomenonof galloping can produce great energy and cause huge harm to the power grid operation.Rapid growth of electricity transmission capacity in China necessitates conductors forhigh-capacity and long-distance and the properties of high flexible of the conductors areeven more prominent. So galloping could bring the conductors of a transmission line closetogether and cause flashovers, even the line breakage or tower crash recently. So, it is veryimportant to study on the galloping for the safe power grid operation. The aerodynamic andgalloping characteristics of the ice-coated lines were studied through the wind tunnel testand numerical simulation. The main contests are as follows:The unstable aerodynamic characteristics which caused by the icing is the culprit ofthe transmission conductors galloping while the research on the icing is essential to solvethe matters.Firstly, the wind tunnel test of the aerodynamic characteristics of the ice-coatedlines was projected according to the typical icing types and the wind field characteristics.The tests were carried out under the uniform flow and the turbulent flow. The differenticing types such as crescent, fan and corona shapes were tested. The influences of theaverage velocity and the two-dimensional flow effect were investigated. The fittingfunctions of the lift coefficients and drag ones were given finally.Secondly, on the issues that the data of the ice-coated transmission conductors, thesimulation of three different icing cross sections under five different icing thicknesses wereproceed based on the Fluent. The reliability of the simulation data was verified according tothe wind tunnel test results. The vertical formulas of different icing cross sections and icingthickness were obtained through the curve fitting technology. The aerodynamiccharacteristics data base of the ice-coated transmission lines were set up.The mathematical model of the one-degree-freedom oscillator of the transmission linewas modeling on account of the theory of quasi-steady state. The multiple scale method was used to solve the amplitude of the oscillator. The numerical simulation program solvingthe time-histories displacement of the oscillator galloping was worked out on account of theRunge-Kutta method. The galloping amplitude results of the multiple scales and theRunge-Kutta method were compared and the accuracy of the multiple scales was satisfied.The influence of the icing cross sections, the icing thickness and the orders of the verticalaerodynamic coefficient functions on the galloping amplitude were discussed. Aiming thehigh-amplitude phenomenon of the galloping, an idea of energy harvesting from thegalloping of the oscillator was proposed. The energy conversion efficiency factor ofdifferent cross section shapes was discussed. Also, the instability of galloping of theone-degree-freedom and two-degree-freedom oscillator models was studied. The formula ofdiscrimination of stability was obtained and the instability of galloping of various cases wasanalyzed.Finally, the finite element model was established which the non-linear dampingelement was fixed to simulate the aerodynamic forces in the ANSYS/LS-DYNA. Thefluctuating wind force was applied on the model and the analysis was carried out to get theresponse of the lines galloping and the towers random vibration. According to the explicitfinite element method proposed above, the wind-induced vibration analysis of the500kVlong span transmission line from Hai-men to Shan-tou was carried out. The bucklingrestrained braces were fixed on the tower for the anti-vibration and different optionalschemes were prosed, then the optimized scheme was got. Also, the anti-gallopingtechnology was investigated, such as the mass block and interphase spacer devices. On thePort Credit test lines, the anti-galloping schemes were proposed and the optimized schemeswere got.