Wind Tunnel Test On Aerodynamic Forces Of Ice Accreted Transmission Lines And Finite Element Analysis On Galloping

Electric utilities is the the lifeblood of the economy, which is related to the aspects of modernization. Then, the transmission line’s building and development is the crucial issues of the electric utilities. In special weather conditions, transmission lines may be iced in windward side, which will complicate the forces. Afterwards, it will cause galloping under specific wind speed and wind attack angle. Galloping is a large amplitude and low-frequency self-excited vibration. The aerodynamic coefficients is the basic data to analysis transmission line’s galloping, which will contribute to the transmission line’s designing and galloping prevention.The icing mechanism, galloping mechanism, galloping prevention were described in this article, and the domestic and foreign wind tunnel test researches on aerodynamic characteristics of iced conductors were reviewed. Aerodynamic characteristics of crescent(4-bundled) and D-shape(2-bundled and6-bundled) conductors were measured by high frequency force balance technique in the wind tunnel. The influence of icing thickness, initial ice accretion angle and sub-conductor on the aerodynamic properties were investigated. The galloping time history and power spectral density function of D-shape6-bundled conductor had been made by FEM.Rigid segment models of D-shaped and4kinds of crescent-shaped were made in the wind tunnel test, 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. And the method to test the aerodynamic coefficient of each sub-conductor were innovative designed. The aerodynamic characteristic varying with wind attach angle were studied, and the influence of icing thickness, initial ice accretion angle and sub-conductor on the aerodynamic properties were investigated. Furthermore, based on the Den Hartog and Nigol’s mechanisms of galloping, the wind angle ranges sensitive to galloping were analyzed.A FEM model was made for the actual transmission line, the tested aerodynamic forces were added to the model and the FEM analysis was made for the iced bundled conductors. A three-node parabola cable element can be used to model the conductor lines and the spacer can be modeled by the Euler beam element. Each sub-conductors of bundled conductor are connected to each other by spacers, and these two elements were connected by the method of DOF polycondensation. The completely Lagrange form of the dynamic equilibrium equation of the cable element was made.The results of this paper enrich the current data of aerodynamic characteristics for iced conductors. And the aerodynamic characteristic varying with wind attach angle were studied, and the influence of icing thickness, initial ice accretion angle and sub-conductor on the aerodynamic properties were studied. It can provide valuable parameters for galloping test and simulation. Moreover, it can also provide a reference for accurately calculating aerodynamic coefficients of other ice-shaped conductors.