Study Of Icing Mechanism And Prevention And Control Strategy Of Power Transmission Line

Icing of power transmission line occurs in special weather conditions result from the phenomenon that supercooled water drops in the atmosphere collide and freeze on conductor surface.Icing on transmission line will increase load bearing and stretch conductors which leads to mechanical injury,breaking down of transmission towers and conductor breaks may happen in serious ice disaster that threatens the safe operation of power transmission line.Therefore,it is necessa ry to analyze the formation mechanism of transmission line icing to predict the growth process based on parameters of meteorology and transmission line.Reasonable icing preventation and control will boost de-icing efficiency as well as mitigate the influence on normal operation of transmission line caused by de-icing work.Motion of the water drops near power transmission line is affected by external forces,thus the icing process will change.For the power transmission lines,water drops will be polarized,and their motion trajectories are governed by both the air flow field and electric field.Moreover,ion flow field is more likely to appear during the icing process on the transmission line surface,this leads to a more complicated electric field.Consequently,i t is necessary to investigate the icing process influenced by ion flow field,which is important for the establishment of ice accretion model.In this work,the ion flow field around transmission line is studied to discover the ice accretion process,a calculation method of ion flow field is presented.Enhanced charge simulation method is used for electric field,2^nd order upwind scheme finite volume method is employed for space charge density.Theseo variables are iteratively calculated until the criterio n is met.Anxperiment is conducted based on corona cage to verify the calculated result.Influcences of voltage level,conductor radius and wind speed on ion flow field are analyzed.According to the solution of ion flow field,ion flow field in presence o f water drops is calculated.For the purpose of analyzing th e ice accretion mechanism,Euler-Lagrange method is used to calculate the trajactories of water drops,then,the accuracy of accretion model is improved.Relative experiment is conductor for the verification of ice accretion model.Joul heat de-icing is a rapidly developing de-icing method,it removes the ice by adding the current of transmission line,the joul heat generated initialize the de-icing process and the ice will begin to melt.In jourl heat de-icing methods,it is nessecary to calculate the de-icing time and de-icing current in accordance to environmental and conductor parametersHeat balance equation is established in line with the analysis of heat transfer process of ice-coated conductor.Critical icing and de-icing conditions are given,and the calculation method of critical icing preventation current and critical de-icing current are calculated.The time cost of de-icing is evaluated combining numerically solved temperature distributi on and the change of geometric shape of the gap inside melting ice.In addition,maximum and minimum de-icing current is calculated in accordance with the heat balance equation and the design requisite of transmission line.Relevant experiment are conducte d to verify the time cost of de-icing.In this work,different joule heat de-icing methods are introduced consists of their theories and applications,and the de-icing strategy is proposed accordingly.The condition of transmission line icing is predicted in line with the weather prognosis,line parameters,the ice accretion model and de-icing current introduced by this work.Additionally,the criterion of ice preventation and de-icing operation and the process of de-icing strategy is presented based on the calculation of de-icing time and de-icing current,the principle is to minimize the power consumption during the de-icing operation.Meteorological parameters of certain period are used as a background to apply and examine the de-icing strategy,besides,to find the optimal de-icing solution.Eventually,practical experiment is conducted in 66 k V transmission line to verify the feasibility of the de-icing method introduced in this paper.In summary,this work studied the ice accretion process and de-icing process,the mechanism of ice accretion affected by ion flow field,thus the ice accretion model will be more accurate.On the other hand,it boosts the the range of the application of de-icing method,enables the calculation in such circumstance where the ice keeps growing in the process of de-icing period.According to the research result,an icing preventation and control scheme is established to determetin the ice preventation and control method between ice preventation method and de-icing method.