Heat Balance Analysis In The Ice Melting Process Of Transmission Lines

Transmission lines icing will cause many problems,such as the load increase of transmission lines,unbalanced tension,galloping and so on,which can lead to large tower collapse,broken line,flash over trips and other serious accidents,which pose a serious threat to the safe and reliable operation of the power system.Therefore,in this paper,a more perfect ice melting model is set up to solve the problem of heat transfer and ice melting of transmission lines,The heat transfer process of the conductor wire is derived from the mechanism of ice melting,the critical ice melting current under different environment and different icing parameters is analyzed and the ice melting time is predicted and verified by experiments.Firstly,according to the conditions of the transmission line ice melting to carry out the research and analysis of the heat conduction of transmission line ice melting,including warming up,twisting and melting three processes.The heat loss of the wire load current Joule heat effect,the wind forced convection,the droplet evaporative heat loss on the wire surface,the thermal energy loss of the droplet collision wire surface kinetic energy,the heat loss of the unfrozen water droplets are also analyzed,And the calculation formula of the critical current of the heat transfer of the transmission line is established.By comparing the effect parameters in the process of ice melting,we can show that the convective heat transfer coefficient of ice surface and the ice thermal conductivity have a significant effect on the thermal equilibrium state of icing.On the one hand,the method of fluid mechanics is used to derive the solution and the variation law of the convective heat transfer coefficient of iced conductor surface(smooth,rough),improving the calculation precision of heat dissipation on the ice surface.On the other hand,this paper designs an experimental platform for the thermal conductivity of icing and the experimental method for ice thermal conductivity.The formula for calculating the thermal conductivity and density of icing is obtained by artificial icing.Critical ice melting current and ice melting time are the most important factors in the actual ice melting engineering.The ice critical ice melting finite element model was established in this paper,the ice thermal conductivity,meteorological parameters and the change of the icing diameter were analyzed.The pressure field,the velocity field,the temperature field and the heat dissipation of the iced conductor were obtained,and the minimum ice melting current is derived according to the heat equilibrium equation of ice melting under steady state.On the other hand,aiming at the thermodynamic ice melting time,according to the physical process of icing conductor melting,simplified calculation formula of the thermodynamic ice melting time is derived and the effects of ambient temperature,ambient wind velocity,ice thickness and ice melting current on the ice melting time were also derived.According to the above theoretical research structure,relying on the National Natural Science Foundation of China,establishing the artificial climate laboratory platform.By adjusting parameters of the artificial climate chamber,the real icing structure such as the glaze ice,soft rime ice,hard rime ice etc was generated and the critical ice melting current and ice melting time were tested under different icing conditions.The simulation results show that the error of the critical ice melting current simulation model in this paper was less than 10%,and the error of the melting time calculation model was less than 15%.The related methods and results have certain reference value to promote the study of the thermal melting ice and improve the safety of the transmission lines.