配电网相电压不对称动态变化下的高阻接地故障辨识  

Identification of High-impedance Ground Faults Under Dynamic Variations of Voltage Unbalance in Distribution Networks

作　　者：李政洋[1] 曹一家 陈春[1] 李妍莎 李景禄[1] LI Zhengyang;CAO Yijia;CHEN Chun;LI Yansha;LI Jinglu(School of Electrical&Information Engineering,Changsha University of Science&Technology,Changsha 410114,Hunan Province,China)

机构地区：[1]长沙理工大学电气与信息工程学院,湖南省长沙市410114

出　　处：《中国电机工程学报》2024年第22期8744-8758,I0005,共16页PROCEEDINGS OF THE CHINESE SOCIETY FOR ELECTRICAL ENGINEERING

基　　金：国家自然科学基金项目联合基金(U1966207);国家自然科学基金项目(52007009)。

摘　　要：配电网单相高阻接地故障与相电压不对称动态变化间具有相似的中性点位移电压波形,易引起接地保护的误判。为此,该文建立不对称导纳矢量模型,通过分析相电压不对称动态变化的原因,揭示非故障条件下中性点位移电压的变化机理。同时建立故障电路全响应模型,刻画中性点位移电压随过渡电阻的变化轨迹,研究高阻接地故障和不对称导纳动态变化时的位移电压稳态重合区域及暂态特征差异。在论证二者稳态特征存在混叠的同时,揭示暂态过程中故障初相角对中性点位移电压直流衰减分量的影响规律。采用经验小波变换提取中性点位移电压直流衰减分量和高频分量,并利用直流衰减分量辨识故障;对于特定故障初相角导致的直流分量无法检测场景,提出基于方差贡献率的重心频率分布特征判断方法辨识接地故障。仿真分析表明,该方法为5 kΩ及以下的高阻接地故障与不对称导纳动态变化提供了明显的区分特征,为单相接地故障的准确辨识提供了新思路。In distribution networks, single-phase high impedance ground faults and dynamically varying asymmetric phase voltages exhibit similar waveforms of neutral point displacement voltage, which can lead to misjudgment of grounding protection. To address this issue, this paper establishes an asymmetric admittance vector model to analyze the causes of dynamically varying asymmetric phase voltages and reveal the changing mechanism of neutral point displacement voltage under non-fault conditions. A full-response fault circuit model is also developed to depict the variation trajectory of neutral point displacement voltage with respect to transition resistance, examining the overlapping steady-state region and transient feature differences between high-impedance ground faults and asymmetric admittance dynamic changes. While demonstrating the overlapping steady-state features of the two, the influence of the initial fault phase angle on the DC decay component of the neutral point displacement voltage during transients is revealed. Empirical wavelet transform is employed to extract the DC decay component and high-frequency component of the neutral point displacement voltage, and the DC decay component is utilized for fault identification. For scenarios where the specific initial fault phase angle renders the DC component undetectable, a centroid frequency distribution feature identification method based on variance contribution ratio is proposed to recognize grounding faults. Simulation analysis indicates that this method provides distinct distinguishing features for high-impedance ground faults below 5 kΩ and asymmetric admittance dynamic changes, offering a new approach for accurate identification of single-phase ground faults.

关 键 词：动态不对称 高阻接地故障辨识 中性点位移电压 直流偏移分量 方差贡献率 

分 类 号：TM77[电气工程—电力系统及自动化]