摘要电力系统的接地网是维护电力系统安全可靠运行、保障运行人员和电气设备安全的重要设备,但往往由于接地网的导体腐蚀、断裂等故障,引起或者扩大事故,带来巨大的经济损失和不良的社会影响。
因此,诊断接地网的断点和腐蚀情况已经成为电力部门的一项重大反事故措施。
根据地网接地引下线之间电阻或者转移电阻的测量值,建立合适的模型,求出地网各段导体的电阻值,进而判断地网是否有断裂或者被腐蚀的导体存在以及它们的位置。
但是受到可及节点数目总是小于地网支路数目的限制,得到的故障诊断方程都是欠定的,而且方程还没有显式的解析表达式,直接求解困难很多。
针对上述问题,本文从模型和求解两方面接地网故障诊断方法做了深入详细的分析和研究。
分析了故障诊断模型的特点,根据矩阵分析的基本理论,考虑用基于遗传算法的最小二乘法来求解诊断方程。
避免了由与简化过程所带来的误差,从而使地网故障诊断方程的以直接求解。
本文建立和求解的数学模型的过程可以分为三步:首先,根据可及节点的数目建立非线性隐式方程;其次,求解非线性约束规划问题,以能量达到最小构造目标函数;最后,将遗传算法引入对非线性故障诊断方程的求解过程中,用遗传算法求出满足目标函数的全局最优解,并收到了良好的效果。
关键词:接地网,故障诊断,遗传算法ABSTRACTThe grounding grids of substations are important equipment to keep stable operation of power system and safety to operator and power apparatus. But the grounding faults due to corrosion of substation grounding grid often take place. The corrosion of these grounding grid and electromotive force of grounding current, can induce grounding grid fault. These grounding grid faults often bring huge economical lost and bad society effect. So how to diagnosis the corrosion condition of grounding grid and its location is a very important measure remained to electric power system to guard against grounding faults.If the relationship between port resistances and conductor resistance is given, conductor resistance can be computed from port resistances through mathematical analysis. Comparing these results with the initial values that they are designed to be, the accurate current corrosion status of all grounding conductors under ground can be known. But the number of those touchable nodes is always fewer than that of the branches, the function we obtain according electric circuit theory is a function which number is fewer than its variable, and they have no explicit analytic expression. To solve the function straightly become very difficult.From above problems, this thesis gives some in-depth and detailed analysis about corrosion of substation grounding grid from its model and solution. After analyzing the characteristics of model, and based on matrix analysis theory, one solution is proposed. That is, we can use implicit function to satisfy all demands from optimization a rithmetics, such as differential coefficient, grids or determinant, which makes sure that simplified errors can be prevent and our model can be solved too. The mathematic models in this thesis can be divided into three parts: part one, to sum up solving the implict equation; part two, to sum up solving a nonlinear constrained optimization problem; part three, bring Genetic Algorithms into solving the model of nonlinear implict equation, and get a good result.KEY WORDS: grounding grid,corrosion diagnosis, Genetic Algorithms目录第1章绪论 (1)1.1 研究问题的工程背景 (1)1.2 国内外研究现状 (2)1.3 本文的主要工作 (3)1.3.1 主要研究内容 (3)1.3.2 论文章节编排 (4)第2章矩阵知识和遗传算法概述 (5)2.1 函数矩阵的基本运算及其性质 (5)2.2 函数矩阵的导数 (7)2.3 遗传算法概述 (9)第3章接地网故障诊断原理及其数学模型 (13)3.1 接地网故障诊断原理 (13)3.2 数学模型 (16)3.2.1 约束规划模型 (16)3.2.2 工程简化模型 (17)3.3 模型分析 (18)3.4 基于遗传算法的非线性最小二乘优化算法 (21)3.4.1 遗传算法的主要实现技术 (22)3.4.2 本文中遗传算法的实现 (24)3.3 本章小结 (25)第4章地网故障诊断实例研究 (27)4.1 算例1 (27)4.2 算例2 (33)4.3 算例3 (36)4.4 本章小结 (39)第5章结论与展望 (41)致谢 (42)参考文献 (43)附录 (45)附录1 (45)附录2 (48)附录3 (53)第1章绪论1.1研究问题的工程背景发电厂、变电站的接地网是保证电力系统安全可靠运行的重要措施。