【作者】 赵有铖；

【导师】 卢继平；

【作者基本信息】 重庆大学 ， 电气工程， 2003， 硕士

【摘要】 配电网量大面广，担负着直接为广大用户供电的任务。随着社会经济的发展，人们对电力的需求日益增长，同时对供电质量提出了更高的要求。因此，有必要对配电网中的异常运行状态进行分析，找出隐患；此外，当发生故障后要能快速有效地检出，保障系统安全、稳定运行和供电可靠性。随着配电网中电缆线路的大量使用，出现基波电流谐振的可能性大大增加，威胁系统的正常运行。文中结合某变电站异常运行状态实例，在理论分析和MATLAB语言数值计算的基础上，指出由于电缆的大量使用导致了该系统参数配合不当，从而诱发了基波电流谐振，并提出装设静态补偿器以防范该类谐振。 应用MATLAB中的电力系统仿真工具箱(SimPowerSystems)建立了相应的动态仿真模型进行详尽的仿真研究。仿真分析结果表明，该方法是行之有效的。配电网中性点采用小电流接地在世界范围内是一种较流行的接地方式，并在我国配电网中得到了广泛应用。小电流接地系统单相接地故障选线是多年来一直未能很好解决的一个难题。文中简要介绍了小波分析的理论基础及其在电力系统中的应用现状，概述了配电网中性点各种接地方式的优劣，系统归纳了现有的各种选线原理和方案的特点，提出了尚需解决的问题，并给出了分析的结论。在详细分析小电流接地系统发生单相接地故障时暂态特征的基础上，提出应用具有多分辨率分析和良好的时频局部化特性的小波变换提取故障暂态信息，实现故障选线的新方法。即利用相应出线相电流或分量的暂态信息突变量在小波变换某一尺度下模极大值或能量比较来确定故障线路，该方法同样适用于只装设两相CT的小电流接地系统，从而克服了迄今为止提出的一些选线方法在系统只装设两相CT时失效的问题。全面讨论了小波基的选取、分解尺度的确定、小波变换的边界处理等几个与算法密切相关的问题。采用基于Stein无偏似然估计自适应阈值选择原理的实用消噪方法对故障信号进行预处理，在改善信噪比的同时，又提高了对突变信息的分辨率。深入细致地分析了谐波、间歇电弧、电流互感器、负荷、过渡电阻等多个因素对故障选线结果的影响，为方案的实用化奠定了基础。理论分析及大量仿真实验证明，本文提出的选线方法准确、可靠，适应性、灵敏性均优于现有的基于稳态量方法，适合各种接地方式的小电流接地系统，具有很好的鲁棒性和可行性。更多还原

【Abstract】 The large amounts of power distribution networks take on the basic task of mains power supply to the widespread consumers. Along with the development of society and economy, the demand for power supply and its quality has increased rapidly in recent years. Consequently, it is necessary to analyze the abnormal state and find out the insulation hidden trouble of distribution networks. Besides, faults should be detected rapidly and effectively in order to guarantee the security, stabilization and reliability. Along with the extensive use of power cable lines in power distribution system, the probability of fundamental frequency resonance has greatly increased. It may endanger the normal operation of the power system. On the basis of theoretical analysis and numerical calculations using MATLAB language combined with a real instance, it is indicated that the improper electrical parameter coordination caused by the abundance of power cable lines result in fundamental frequency current resonance, in addition, the countermeasures based on SVC to solve the problem are put forward. Digital simulation results have proved the effectiveness and practicability of the scheme.Small current grounding power system is a popular neutral grounding mode around the world and is widely used in our country. The fault line selection matter in such system is one of the problems, which have not solved successfully for many years.Wavelet analysis theory and its application in power system have been introduced briefly. This paper gives a general overview of various neutral grounding modes. Some existing theories schemes on the fault line selection have been summarized systematically. Then, it presents problems, which should be solved, and conclusions have been made.The fault transient characteristics of single-to-earth fault for small current grounding power system are analyzed in detail, and then a novel algorithm for fault line selection is put forward. This method uses wavelet transform to pick up the transient fault information because of its multi-resolution characteristics and time-frequency localization nature. Fault line is detected based on the modulus maxima or energy comparison under some scale of wavelet transform of phase currents orβcomponent current. This method is applicable for such power system as only furnished with CT on two phases, so the shortcoming of other methods presented in recent years is overcome. Some issues associated with the algorithm such as wavelet function selection, analysis level, and boundary treatment and so forth have been discussed. The stein self-adapting threshold denoising method is used to the signal pretreatment, thus the SNR and resolution are improved. The influences of several factors such as harmonics, intermittent arc grounding, CT, load and fault resistance have been thoroughly analyzed, therefore, it is fundamental work for its application.Theoretical analysis and a variety of simulation results show that the proposed method is accurate and reliable, its applicability and sensitivity are better than the steady method. It is suited for various small current grounding system, furthermore, the robustness and feasibility of this scheme is also testified.更多还原