【作者】 陈凌；

【导师】 蒋兴良；

【作者基本信息】 重庆大学 ， 电气工程， 2011， 博士

【摘要】 覆冰严重威胁着输电线路的安全稳定运行,自上世纪五十年代以来,我国输电线路的覆冰事故时有发生。特别是2008年初,南方地区大面积发生了有气象记录以来的最严重冰灾,给电力系统造成了严重破坏,给国家电网及南方电网造成了极大的经济损失,给人民生产、生活带来极大的不便。造成我国输电线路覆冰事故频发的原因主要有:对输电线路覆冰问题认识不足,重视不够,从而导致针对线路覆冰规律的基础研究工作的缺乏;缺乏能及时掌握线路覆冰过程的有效手段;防冰、除冰应急措施研究不够。2008冰灾之后国家投入了大量的人力、物力和财力研究输电线路覆冰问题。研究不同环境条件下的覆冰增长规律和有效的线路覆冰过程预测方法,对线路覆冰后及时采取合理的处理措施避免重大冰害事故的发生有着非常重要的意义。覆冰参数是覆冰研究的基础,研究者提出的众多覆冰预测模型都是基于覆冰过程中的覆冰参数的,然而对于覆冰参数的测量是一直都没有得到很好解决的难题,因此研究覆冰过程中的覆冰参数预测有着较大的学术意义及工程应用价值,本论文的主要工作如下:基于流体力学原理,采用数值计算对覆冰过程中的过冷却水滴碰撞特性进行了研究,得到了水滴-气流二相流的运动轨迹、速度场、及覆冰圆柱体上水滴碰撞速度分布规律等;并深入分析研究了影响过冷却水滴碰撞率的因素及其影响规律。研究结果表明,水滴碰撞率是风速、水滴大小及圆柱直径的函数。根据大量数值计算结果提出了新的碰撞率解析计算公式,与现有公式相比精度得到了较大的提高;基于热平衡模型,研究了过冷却水滴在覆冰表面的冻结特性,经推导得到了冻结系数的计算公式,并通过仿真计算深入的分析研究了影响覆冰过程中冻结系数的影响因素及影响规律;以碰撞过程及冻结过程为基础提出了旋转圆柱体的覆冰增长模型。设计了用于覆冰参数预测用的旋转多圆柱积冰器,并在大型多功能人工气候室内通过改变覆冰时间、环境温度、风速等参数对旋转多圆柱积冰器进行了大量的人工覆冰试验,对旋转圆柱体覆冰增长模型进行了验证;同时采用仿真与试验研究相结合的方式,研究了覆冰参数对覆冰量的影响规律,结果表明根据模型仿真计算得到的覆冰参数对覆冰量的影响规律与试验结果基本一致。根据旋转圆柱覆冰增长模型建立了旋转多圆柱体上覆冰量与覆冰参数关系的非线性方程组;提出了基于旋转多圆柱体上覆冰量变化,利用建立的方程组来预测覆冰过程中的覆冰参数;基于自适应的思想对差分进化算法进行了改进,并利用改进的差分进化算法对方程组进行求解从而实现了覆冰参数的预测。采用这种方法对人工气候实验室内覆冰过程的覆冰参数进行了预测,利用激光粒度分析仪、风速仪、温度仪对覆冰参数(液态水含量、水滴中值体积直径、风速、温度)进行了验证,结果表明预测结果与实测结果基本吻合。在雪峰山自然覆冰站,根据旋转圆柱体上的覆冰量变化对某次覆冰过程的等效覆冰参数进行了预测,并根据预测得到的等效覆冰参数对覆冰试验导线的覆冰量进行了估算,总的来说还是能反映导线的覆冰增长过程。更多还原

【Abstract】 Icing is a great threat to the secure and stable operation of transmission lines. The icing accidents on transmission lines have occurred frequently in China since the fiftieth of last century. Especially at the beginning of 2008, the most serious icing disaster in the meteorologic history occurred in large areas of south China. This distaster caused great economic losses to the Sate Grid Corporation and China Southern Power Grid Corporation by the heavy damage of power system which brought great inconvenience to people’s production and living. The main reasons of frequent icing accidents in our power system are as the follows: the icing problem in power systme did not get enough attention, which leads the lack of basic researches on the rule of icing; effective measures for monitoring the process of ice accretion on transmission lines is lack; the researches on emergency measures of anti-icing and de-cing is short. After the icing disaster in 2008, China has invested a great deal of manpower, material and financial resources to the researches on icing.Researches on the rule of ice accretion on transmission lines and on the effective measures for forecasting the ice accretion are of great significance for avoiding the grave icing accident by adopting reasonable measures in time. The icing parameters are the basis of the icing researcheas, but the measurement of icing parameters is a difficult problem which has not been solved yet. So the research on the forecast of icing parmaters is of important academic significance and engineering practical worthiness. The main work in this paper is as follows.Based on the principle of hydrodynamics, the paper researches the collision characteristics of supercooled droplets using the numerical calculation. The motion trails of droplets and air flow, velocity fiels of droplets and air flow, and the distribution of collision speed on icing cylinder are obtained. The paper also researches the influencing factors and their effect on collision efficiency, and research results show that the collision efficiency is a function of air speed, diameters of droplet and icing cylinder. Accord to the large number of numerical calculation results, the paper gives a new analytical formula for calculating collision efficiency, and this formula is more precise compared to others’formulas. Based on the heat balance model, the paper derives the formula for calculating freezing fraction. The paper also researches the influencing factors of freezing fraction and their influence on freezing fraction. Combining the processes of collision and freeze, the paper gives the ice accretion model for the rotating cylinder.The paper designs a rotating multi-cylinders ice collector used for forecasting icing perameters. And by changing the icing parameters such as icing duration, ambient temperature, air speed etc in multi-function artificial climate chamber, the paper conducts a good deal of experimental researches to verify the ice accretion model of roating cylinder. At the same time, the influence of icing parameters on ice amount is reasearched by simulation and experiments. The results show that the influence of icing parameters on ice amount obtained by model’s simulation agrees well with that obtained by experiments.The paper builds the non-linear equation set between ice amount on rotating multi-cylinders and the icing parameters according to the model of ice accretion on rotation cylinder. And the paper proposes that using the equation set to forecasting the icing parameters according to the ice amount change on rotating multi-cylinders. This paper also improves the differential evolution algorithm and uses this algorithm to solve the equation set. The icing parameters in artifical climate chamber are forecasted by this method, the forecasted results are verified by laser particle size analyzer, anemobiagraph and thermograph. And the results show that the forecasting values agree well with the experimental values.According to the ice amount on rotating multi-cylinders, the paper forecasted the equivalent icing parameters in an icing event at Natural Icing Station on Xuefeng Mountain. And using these icing paramters, the papar evaluated the ice amount on expeirmental conductors. The comparsion of the evaluated values and the measured values show that the evaluated ones are larger than the measured ones, but in general, the evaluated ice amount can reflect the ice accretion on conductors.更多还原