【作者】 罗涛；

【导师】 陈民铀；

【作者基本信息】 重庆大学 ， 电气工程， 2009， 硕士

【摘要】 随着电气设备容量的扩大和社会对电力需求的日益增长,对输电线路的可靠性要求也不断提高。在电能的传输过程中,电力电缆作为主要载体被广泛的使用。由于在敷设过程中选用理论数据设计电缆回路,使得电缆回路的理论载流量和实际运行中表现出的载流量有较大的差异,如何对现有运行电缆的载流量在不同条件下的变化情况进行分析,对于提高电缆的容量利用率,准确快速的计算其载流量对电力系统安全、可靠、高效地运行有着很重要的意义。电缆绝缘层的工作温度不能超过其耐热寿命允许值。由于影响电缆散热的可变因素很多,仅按规程法确定载流量无法满足需要。为保证电缆安全、有效地运行,采用数值计算方法精确模拟地下电缆的散热特性具有重要的工程实际意义。本文在理解温度场的基础上,将地下电缆温度场归结为二维热传导问题,建立了地下电缆的温度场的控制方程、影响范围以及边界的边界条件。对二维传热方程组使用有限元法进行离散。使用有限元分析软件COMSOL作为软件平台,建立了各种敷设形式的地下电缆温度场的模型,结合双点弦截的迭代方法快速准确的计算各种地下电缆的最大载流量,对比规则和不规则排列情况下地下电缆的温度场分布,并详尽的分析了各种因素对地下电缆载流量的影响,为地下电缆安全、可靠地运行提供保障。同时,建立了地下电缆的电场模型,得出电缆电场的分布,与温度场得出的数据进行比较,分析两者间的数值关系。计算结果表明电缆的温度场与电场之间呈近似的线性关系。为更好对地下电缆的运行状态进行监测提供了新的思路。更多还原

【Abstract】 With the increase of electrical equipments’capacity and the growing electricity demand of society, the reliability requirement of transmission line is required higher and higher. In the process of power transmission, power cables are widely used as the main carrier for power transmission. In the cable laying process, the data are selected to design cable circuit, which leads to the cable circuit’s theoretical and practical carrying capacity have a great difference. So how to analyze the carrying capacity of present running cables under various conditions is very important to improve cables’capacity utilization rate, to calculate its carrying capacity rapidly and accurately, to guarantee the power system safety, reliability and high efficiency.The operating temperature of the cable insulation layer should not exceed the allowable values of its heat-resistant life. It will not meet the demand if the carrying capacity is only determined by rules because of excessive variable factors that affect the heat dissipation of cables. To ensure the cable safety and operation effectiveness, the use of accurate numerical method to simulate the heat dissipation characteristics of underground cables has great practical significance.On the basis of temperature field, in this paper, the temperature field of underground cables was treated as two-dimensional heat conduction problem, the control equation, area and the boundary condition of the temperature field of the underground cable were established. The finite element method was used to discrete the two-dimensional heat transfer equations. The finite element analysis software COMSOL was used as a software platform to build the various forms of laying underground cable models of temperature field, at the same time,using the dual-point secant method to calculate the underground cables ampacity rapidly and accurately , comparing to the rules and irregularity the rules of underground cables with the temperature distribution, and detailed analysis of the various factors on the impact of ampacity for protecting the safety and reliable operation of underground cables was given.At the same time, the electric field model of underground cables was established to obtain the the distribution of electric field and the the data was compared with the data from the temperature field to analyze the numerical relationship. The computa- tional results showed that the temperature field is linear with the electric field. The conclusion provide new solution for the state monitoring of the underground cables.更多还原