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-circular cross section. Galloping of ice-coated transmission conductors is a high-amplitude and low-frequency self-excited vibration. The large displacements induced by the phenomenon of galloping can produce great energy and cause huge harm to the power grid operation. Rapid growth of electricity transmission capacity in China necessitates conductors for high-capacity and long-distance and the properties of high flexible of the conductors are even more prominent. So galloping could bring the conductors of a transmission line close together and cause flashovers, even the line breakage or tower crash recently. So, it is very important to study on the galloping for the safe power grid operation. The aerodynamic and galloping characteristics of the ice-coated lines were studied through the wind tunnel test and numerical simulation. The main contests are as follows:The unstable aerodynamic characteristics which caused by the icing is the culprit of the transmission conductors galloping while the research on the icing is essential to solve the matters.Firstly, the wind tunnel test of the aerodynamic characteristics of the ice-coated lines 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 different icing types such as crescent, fan and corona shapes were tested. The influences of the average velocity and the two-dimensional flow effect were investigated. The fitting functions of the lift coefficients and drag ones were given finally.Secondly, on the issues that the data of the ice-coated transmission conductors, the simulation of three different icing cross sections under five different icing thicknesses were proceed based on the Fluent. The reliability of the simulation data was verified according to the wind tunnel test results. The vertical formulas of different icing cross sections and icing thickness were obtained through the curve fitting technology. The aerodynamic characteristics data base of the ice-coated transmission lines were set up.The mathematical model of the one-degree-freedom oscillator of the transmission line was 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 solving the time-histories displacement of the oscillator galloping was worked out on account of the Runge-Kutta method. The galloping amplitude results of the multiple scales and the Runge-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 vertical aerodynamic coefficient functions on the galloping amplitude were discussed. Aiming the high-amplitude phenomenon of the galloping, an idea of energy harvesting from the galloping of the oscillator was proposed. The energy conversion efficiency factor of different cross section shapes was discussed. Also, the instability of galloping of the one-degree-freedom and two-degree-freedom oscillator models was studied. The formula of discrimination of stability was obtained and the instability of galloping of various cases was analyzed.Finally, the finite element model was established which the non-linear damping element was fixed to simulate the aerodynamic forces in the ANSYS/LS-DYNA. The fluctuating wind force was applied on the model and the analysis was carried out to get the response of the lines galloping and the towers random vibration. According to the explicit finite element method proposed above, the wind-induced vibration analysis of the500kV long span transmission line from Hai-men to Shan-tou was carried out. The buckling restrained braces were fixed on the tower for the anti-vibration and different optional schemes were prosed, then the optimized scheme was got. Also, the anti-galloping technology was investigated, such as the mass block and interphase spacer devices. On the Port Credit test lines, the anti-galloping schemes were proposed and the optimized schemes were got.