Wind Tunnel And Numerical Study On Aerodynamic Characteristics Of Ice Accreted Transmission Lines

In special weather conditions, transmission lines may be iced in windward side, with some features of the wing. It may cause a large amplitude and low-frequency self-excited vibration, which is so called galloping. In recent years, with the rapid development of the power systems and frequent occurrence of the extreme weather, the galloping due to the icing and snowing of the transmission lines has been a serious threat to the security of the electricity and communication network operations. The aerodynamic parameter of the iced conductor is a key factor that affects the calculation and analysis for dancing. Although there have been some test results of the aerodynamic parameter, due to the randomness and variability of the accreted shape, the data for anti-galloping design has not been obtained enough and there is a great value to accumulate more aerodynamic parameters of iced conductors.In this study, the domestic and foreign wind tunnel test researches on aerodynamic characteristics of iced conductors were reviewed in detail, and the shortcomings and inadequacies were proposed. Then the aerodynamic characteristics of single and multi-bundled conductors with difference thickness crescent-shaped and D-shaped were studied by wind tunnel test and numerical simulation (CFD). The main contents of the wind tunnel test and numerical study were as follows:Wind tunnel test:Rigid segment models of D-shaped and 4 kinds of crescent-shaped were made, and the aerodynamic characteristics were then measured by high-frequency force balance. A wind tunnel test device taking the two-dimensional flow characteristics and the effect of boundary layer into account was designed. Under the homogeneous turbulence of 0%,5% and 13%, the aerodynamic force coefficients of single and bundled conductors with different ice section were obtained, and the effects of turbulence on the aerodynamics were discussed. Subsequently, the relationships between the aerodynamic characteristics of single conductors and those of bundled conductors were described. Furthermore, based on the Den Hartog and Nigol's mechanisms of galloping, the wind angle ranges sensitive to galloping were analyzed.Numerical study. Wind flow around a cylinder with Reynolds number of 3900 was simulated adopting LES. The effects of near-wall grids and span-wise length on the numerical result were studied in detail. The aerodynamic coefficients of single and 4-bundled conductors with thin crescent-shaped ice were then calculated by k-ωSST turbulence model. The parameters such as span-wise length, grid size and turbulence model, which affect the calculation result were discussed. By comparisons of numerical results with those of corresponding experiments, the appropriate numerical model was verified. While the wind tunnel test is only able to obtain the overall moment coefficients of 4-bundled conductors, numerical study is capable of quantifying three parts of torsion on the bundle conductors respectively.The results of this paper enrich the current data of aerodynamic characteristics for iced conductors. It can provide valuable parameters for studying on galloping test and simulation. Moreover, it can provide a reference for accurately calculating aerodynamic coefficients of other ice-shaped conductors.