Research On Key Factors Of Ice Growth And Influence Mechanism For Transmission Conductor

The ice such as the freezing rain,fog,etc.will change the load and insulation characteristics of transmission lines,which will cause the conductor breaking,the tower collapsing and the insulation flashover which result in the great damage of transmission lines.In order to effectively improve the accuracy of icing prediction,it is very important to establish a practical anti-icing and deicing strategy and establish accurate icing model.Icing is the physical process of droplet impact in the air to the latent heat curing of the conductor.The core content of the growth model is the calculation of the coefficient of overcooling droplet collision and the coefficient of freezing.The collision coefficient is the key parameter to predict the growth of conductor icing.In this paper,a typical ice model is established based on the common ice profile and then according to the standard turbulence model of gas-liquid two-phase flow and the Euler-Lagrangian principle,the mathematical model of the external two-dimensional flow field is established to realize the simulation of collision coefficient,then the collision coefficients of elliptical and winged ice are obtained respectively under different wind attack angles.The simulation result shows that the collision coefficient of circular cross section iced conductors is 4.79%-6.21% higher than elliptical icing with an axial ratio of 4:3 and 4.04%-8.14% higher than wing shape icing under the same weather conditions.However,because of the complexity of above method,an intelligent forecasting method based BP on neural network is proposed which mainly includes following steps: firstly,the large amounts of data are obtained by the simulation,then,the nonlinear relationship between input and output is fitted combing with BP neural network algorithm,finally,the collision coefficient of the given input is predicted by the man-machine interaction platform.The results show that the method is fast and efficient,and the error is less than 9%.The freezing fraction is calculated by the equation of the surface heat balance of the ice,and the convective heat transfer coefficient is the core parameter of the heat balance equation.Taking into account some of the characters of the natural icing such as non-circular cross-section and rough surface,the traditional empirical formula has cannot be directly applied.The hydrodynamics has been adopted to get the temperature field of the surface of the ice and the variation law of the convective heat transfer coefficient of the surface in this paper.The simulation results demonstrate that,apart from the working condition of the low Reynolds number,the greater the equivalent roughness height,the greater the convective heat transfer coefficient,and the surface heat transfer coefficient is also influenced by the cross-sectional shape and the icicle configuration mode,The convective heat transfer coefficient of the wing section is greater than that of the circular section and the oval cross section under the same meteorological conditions.Finally,the collision and convective heat transfer test in artificial microclimate laboratory are fulfilled,and the comparison of the test data with the simulation used to verify the simulation method.Meanwhile,the icing growth process was carried out,and the influence of the parameters such as weather and conductor structure on the icing process was observed from the real angle.