【作者】 李志勇；

【导师】 张化光；

【作者基本信息】 东北大学 ， 电力系统及其自动化， 2010， 硕士

【摘要】 随着电力系统的迅速发展,国内外中低压配电网广泛的采用中性点不接地和经消弧线圈接地的方式来保证供电系统的可靠性。面临着越来越多的电能质量需求和环境影响等多方面的要求,当发生单相接地故障时,快速的发出报警信息并选择出故障线路变得尤为重要。虽然,现在已有很多的选线报警设备应用在系统中,但是实际的运行效果不是很好,选线准确率一直不高。本文针对配电网单相接地故障时的特点,在总结分析了前人选线采用的方法和故障线路暂态电气量特征的理论基础上,提出了基于小波包变换和ARMA模型的配电网单相接地故障选线方法,通过计算机仿真软件MATLAB(Simulink)的仿真结果得出了选线方法的理论有效性。本文在分析了配电网单相接地故障时电气量的暂、稳态特征基础上,根据故障时暂态零序电流的数据特征,提出了应用时间序列分析ARMA模型来重新构造故障时的零序电流思想,进而提出了高性能的选线方法。本文利用小波包具有的低频部分和高频部分同时进行分解去噪的特点,选择db8的小波基函数对暂态零序电流信号进行消噪预处理工作。采用时间序列分析ARMA模型对预处理后的信号进行离群性特征分析,重新构造线路的零序电流信号,并同时得到其相应的暂态响应曲线。提出了根据重构后的零序电流幅值和相位的不同作为选线的主判据,利用重构后零序电流暂态响应幅值的不同作为辅助判据的选线方法来达到选线目的。最后,本文通过MATLAB(Simulink)仿真软件构建10KV的配电网仿真模型,采用其小波工具箱(Wavelet Toolsbox)和系统辨识工具箱(System Identification Toolbox)对不同的故障接地电阻及故障点进行了大量的仿真分析,验证了本文提出的选线方法的理论有效性,且该方法受故障点位置、故障电阻等因素影响较小,具有可靠性高、抗干扰能力强的特点,适用于中性点不接地和经消弧线圈接地的配电网单相接地故障选线,具有重要的理论意义和实用价值。更多还原

【Abstract】 With the rapid development of power system, in order to ensure the reliability of power supply system, many medium and low voltage distribution networks in the world use neutral point un-earth system and resonant grounded system. Facing to more and more requirements, such as demands of power quality and environmental influences, it was very important to send alarm information to control center and select the exact fault line when a single phase-to-ground fault happens. Though there are always line selection and alarm equipments consists in many power systems, they offen run with very low efficeincy of line selection. To the characteristics of single phase-to-ground fault of distribution network, this thesis proposed a method of detecting single phase-to-ground fault for distribution network based on wavelet packer transform and ARMA models, by summarizing and analyzing the methods used before and the characteristics of transient quantity of electricity in the fault line. And the simulation results verified the proposed method by the software of MATLAB (Simulink).Based on the analysis of the transient and steady characteristics of quantity of electricity, this thesis proposed an idea of reconstructing the zero-sequence-current and method of line-selecting during falt occures according to its data characteristics. Since the wavelet packer can do the decomposition and denoising for both the low frequency signal part and high frequency signal part at the same time, db8basis function of wavelet was chose to do the denoising pretreatment. And the signal’s outliers is analyzed and the zero-sequence current signal is obtained by time series analysing ARMA model, and the corresponding transient response curve was also obtained. According to the different amplitude and phase of refitting zero-sequence current as the main criterion for line-selecting, and its different amplitude of transient response as auxiliary criteria for the line-selecting to complete fault line selection function. Finally, this thesis constructed a10kv distribution network simulation model through the simulation software of MATLAB(Simulink). For the different fault resistance and fault location, this thesis carried out a lot of simulations and analysis through the Wavelet Toolsbox and the System Identification Toolbox. The results of simulations verified the validity of the line-selecting method. And we can also get the conclusion that the proposed method has great ability of anti-interference with different fault positions or fault resistences. The method is suitable to nertral ungrounded system and neutral earth with an arc suppression coil system, it’s important to theory significance and practical value.更多还原