发电机定子绕组单相接地保护自适应判据研究

分析了发电机机端和中性点的零序基波及3次谐波电压故障暂态分量的特点,在此基础上提出了发电机定子绕组单相接地保护的自适应判据。该判据考虑了零序基波电压及3次谐波电压故障分量的综合效应,并以制动信号谱能量和动作信号谱能量的比值作为制动系数,该值在发电机正常运行时接近为1,在发电机定子绕组单相接地时远小于1。因此,自适应判据有效提高了保护在定子绕组经过渡电阻单相接地情况下的灵敏度。文章还建立了发电机的多回路暂态数学模型,采用半隐格式求解法对定子单相接地故障进行了仿真,结果证明了所提判据的有效性和良好的抗噪性。     

基于3次谐波电压故障暂态分量的定子单相接地保护

在分析发电机定子单相接地故障产生的故障暂态分量信息特征的基础上，提出了一种定子单相接地暂态保护方案。该保护方案根据单相接地故障后机端和中性点3次谐波电压的故障暂态分量近似相同的特点，把两个故障分量的相量和与相量差分别作为保护动作信号及制动信号，通过比较数据窗内相应信号的谱能量检测定子单相接地故障。仿真和试验结果表明新的暂态保护判据灵敏度高，不受发电机运行工况的影响，具有较好的鲁棒性。     

大型汽轮发电机定子单相接地故障定位新方法

发电机定子绕组单相接地故障定位能扩展目前定子接地保护的功能,为快速检修故障提供依据。分析了大型汽轮发电机的电动势分布特征,推导了定子绕组电势与故障位置的关系,给出了新的定子绕组电势表达式。分析了定子绕组单相接地故障时零序电压、三相电压的幅值变化特征,推导了三相电压幅值变化与故障位置和接地电阻的关系。在此基础上,提出了一种综合利用零序电压和三相电压幅值特征的定子绕组单相接地故障定位新原理。理论分析和仿真计算表明:应用本方法能可靠识别故障位置,且该方法不受中性点接地方式的影响。该方案仅需要零序电压和机端三相电压,简单易行,不需增加额外设备,适用于高阻接地故障,仿真数据验证了算法的可行性。     

基于零序电压故障暂态分量的发电机定子单相接地保护方案研究

根据发电机发生定子单相接地故障后机端和中性点零序电压故障暂态分量近似相同的特点，提出了两种形式的基于零序电压故障暂态分量的发电机定子单相接地保护方案：第一种形式将基波零序电压与三次谐波电压分开处理；第二种形式无需将两者分开，直接把机端和中性点两侧零序电压故障暂态分量的和与差做为保护动作信号与制动信号，通过比较相应信号的谱能量大小检测定子单相接地故障。文中给出了第二种判据形式的详细仿真和试验结果，分析表明：新的暂态保护判据具有很高的灵敏度和可靠性。     

基于多源信息融合的配电网故障选线新方法

配电网小电流接地系统单相接地故障频发且故障信号特征微弱,导致现有的故障选线方法效果欠佳。利用S变换强大时频分析能力对单相接地故障的零序电流暂态特性进行分析,根据能量最大值原则确定特征频带,提取各条线路特征频带下的零序有功能量特征、S变换暂态能量特征和S变换综合相角特征等故障特征量作为输入量,结合最小二乘法支持向量机分类算法的数据融合特性,建立配电网故障选线保护新方案。仿真结果证明了所提方法的有效性。     

发电机定子绕组接地保护3U_0整定

介绍了大型发电机组定子接地保护的作用和目前使用的定子接地保护整定方法。分析计算在各种运行条件下,主变高压侧发生单相接地故障时耦合至发电机侧的零序电压,通过计算发电机单相接地时的接地电流,结合《导则》及省电力技术监督办公室文件,提出了发电机定子接地保护的整定建议。     

基于小波变换的选择性发电机100%定子单相接地保护方案

提出了基于小波变换的选择性发电机100％定子单相接地保护方案。通过直接对机端、中性点两侧的零序测量电压以及零序电流进行小波分析，利用模极大值的极性比较，能可靠地识别出发电机内、外部的定子接地故障，并对内部故障有100％的保护范围。仿真结果表明，新方案在各种运行方式下均能取得很高的保护灵敏度和可靠性，是一种较佳的具有选择性的发电机定子接地保护新方案。     

基于时频矩阵相似度的输电线路暂态保护方法

为提高传统暂态保护方法的可靠性,综合运用宽频带暂态信号在时域和频域上的故障信息,提出一种输电线路保护新方法。该方法利用S变换提取宽频带暂态信号在不同时段不同频带下的故障信息,通过构造时频矩阵来反映暂态信号的时频变化特性;利用奇异值分解提取时频矩阵的时频特征,并减少矩阵冗余量;将奇异值矩阵与样本库矩阵进行时频特征匹配,计算矩阵相似度;根据矩阵相似度判别区内外故障。仿真结果表明,该暂态保护方法能准确快速识别区内外故障。     

基于广义S变换能量相对熵的小电流接地系统故障区段定位方法

小电流接地系统发生单相接地故障后,系统中产生特征较为丰富的电气暂态量。针对健全区段两端的暂态零序电流相似度高,而故障区段两端暂态零序电流差异较大的特点,提出一种基于暂态零序电流的广义S变换能量相对熵的故障区段定位方法。首先,以暂态零序电流作为故障特征量,根据零序电流突变量确定各检测装置上传数据的起始时刻。然后,对馈线上各装置上传的暂态零序电流进行广义S变换,得到其时频矩阵。最后,利用能量相对熵表征各区段两端信号的差异,通过计算比较,确定熵值最大的区段为故障区段。该区段定位方法适用于不同故障点位置、不同故障角、不同过渡电阻情形下的故障定位,仿真结果验证了所提方法的有效性。     

新型发电机100%定子单相接地保护方案

提出了基于B样条半正交小波的新型发电机定子单相接地保护方案。通过直接对机端和中性点两侧的测量电压进行小波变换，无需对测量电压中基波零序和三次谐波零序电压进行算法分离，利用其合成量的小波分析结果，可靠识别出发电机定子接地故障。由于综合利用了故障电压的突变奇异性，新方案能保护100%范围的定子绕组，灵敏度也大大提高。仿真研究和动模试验均表明，该方案在各种运行方式（包括强励）下均能取得很好的保护性能。     

Stator winding single-phase grounding faults protective scheme based on discriminant analysis for Powerformers with selectivity

In order to improve the stator winding single-phase grounding faults protective scheme for Powerformers, a protective scheme based on Mahal distance discriminant theory is proposed in this paper. By the proposed scheme, the different kinds of fault signals can be integrated. Also, a discriminant analysis model for stator winding single-phase grounding faults is established. In the proposed discriminant analysis model, four parameters including the magnitude of leakage current, the direction of leakage current, the magnitude of zero-sequence current in Powerformer terminal, and the direction of zero-sequence current in Powerformer terminal are selected as the discrimination factor. The method of back substitution estimation is introduced to verify the stability of the distance discriminant analysis model. Twenty-five groups of detected samples were analyzed based on the proposed model. The results are consistent with the measured data and show that the distance discriminant analysis model is with higher accuracy and lower mistake-discrimination ratio.     

Features-clustering-based earth fault detection using singular-value decomposition and fuzzy c-means in resonant grounding distribution systems

The transient zero-sequence current of each feeder in a resonant grounding system is characterized by nonlinearity and nonstationarity when a single-phase-to-ground fault occurs. Because there is a significant difference between the fault transient zero-sequence current waveforms of the fault feeder and the sound feeders, a new fault feeder detection method is presented, based on a time-frequency matrix (TFM) and polarity distribution matrix (PDM) singular values clustering algorithm. By applying a Hilbert-Huang transform band-pass filter and waveform transformation to the transient zero-sequence current waveform of each feeder, the TFM and PDM can be constructed, which are decomposed by singular-value decomposition (SVD). Moreover, the normalized singular values of the TFM and PDM are merged together and are used to form the amplitude-polarity feature matrix (APFM). Thus, the feature quantities including the amplitude and polarity information of each fault transient zero-sequence current waveform are obtained. Then, fuzzy c-means clustering is applied to the APFM so as to detect the fault feeder by dividing the fault feeder and sound feeders into two categories without a certain threshold setting. Simulations were carried out via PACAD/EMTDC® and a physical system under various kinds of fault conditions and factors including asynchronous sample, two-point-grounding fault, and arc fault. Simulated results show that the proposed method has the characteristics of high accuracy and reliability in earth fault feeder detection.     

A selective single-phase-to-ground fault protection for neutral un-effectively grounded systems

Single-phase-to-ground faults are the most frequent faults likely to occur in power distribution networks. As for a neutral un-effectively grounded system (NUGS), the low fault current is very common in the case of occurrence of a single-phase earth fault, leading to hard identification of the faulty feeder. In conventional way, this target can be possibly achieved by the comparison of the polarities, magnitudes, or the phase angles of the zero-sequence currents of all feeders connected to the same busbar. However, it becomes a difficult task to implement this functionality into the protection of feeder. In this paper, a novel single-phase-to-ground fault protection for NUGS is put forward. Different from conventional centralized-comparison protection, this protection can detect single-phase-to-ground fault on the feeder individually, and can be realized on FTU (Feeder Terminal Unit). It is based on the measurement of the zero-sequence voltage and zero-sequence current. The tripping strategy follows the characteristic of the modified inverse-time delay curve. By means of analyzing the characteristics of the zero-sequence transient currents, it is disclosed that the magnitude of the zero-sequence current of the faulty feeder should be greater than that of any sound feeder. Then a composite compensated voltage is formed based on the zero-sequence voltage and zero-sequence current to evaluate a revising factor for every feeder respectively. Using this revising factor to modify the identical standard inverse-time delay curve adopted by all the feeder zero-sequence overvoltage protections, the tripping time of the zero-sequence overvoltage protections of all feeders will differ from each other. In this case, the selectivity of the protection can be guaranteed. This proposed algorithm is validated with the EMTP simulation tests.     

应用故障暂态特性实现配电网故障选线的新方法

通过研究谐振接地电网中零序信号的暂态特性,建立了零序电流信号频谱能量分布与故障发生时刻、接地点过渡电阻之间的关系.在利用小波包对暂态零序信号进行分解的基础上,给出了能量比因子和暂态因子的定义,提出了基于以上两个因子取值的自适应故障选线方法.该方法充分利用了暂态零序信号中的低频、工频和高频信息,自适应地选择在故障特征最明显的频带中进行选线,对母线和高阻接地故障均有良好的灵敏性和可靠性.理论分析与仿真结果证明所述方法正确、可行,可实现无死区的故障选线.     

小电阻接地配电网多回线故障分析与自适应零序电流保护

当小电阻接地配电网发生同母多回线接地故障时,每条馈线的零序电流相比于单回线故障时有较大差别,馈线零序电流保护可能不正确动作。为此,首先推导了发生多回线同名相单相接地与单回线单相接地故障时馈线零序电流间的关系,揭示了保护不正确动作机理。提出了考虑负荷且能适用于不同类型多回线接地故障的零序电流计算方法。基于实际变电站参数搭建RTDS仿真模型,分析了不同类型多回线接地故障对零序电流保护的影响。在此基础上,提出了自适应馈线零序电流保护方案,利用故障前电压等参数将发生多回线接地故障时的零序电流修正为发生单回线接地故障时的零序电流,在不改变原有保护定值的情况下使零序电流保护能够自主适应于不同类型的多回线接地故障。基于RTDS和自主研发的保护测控装置的测试结果表明,所提保护方案不受负荷电流的影响,能够在不同类型的多回线接地故障发生时正确动作,且能够提高馈线零序电流保护对过渡电阻的耐受能力。     

Novel protection scheme of stator single-phase-to-ground fault for powerformers

This paper presents a novel stator single-phase-to-ground fault protection of Powerformer in parallel based on the fuzzy clustering algorithms. First, the direction and magnitude of zero-sequence current and leakage current are analyzed, and four fault characters are selected as historical data. Then the historical data are divided into two groups by fuzzy clustering algorithms, and cluster center of each group is calculated. The space relative distance among detected pattern and two cluster centers is finally calculated to discriminate the faulty Powerformer. Simulation results have shown that, under different fault conditions, the new scheme can distinguish reliably internal faults from external faults, and can detect stator single-phase-to-ground fault occurred in which Powerformer with resistance 5 kΩ. A 100% of the winding can be fully protected.     

配电网单相接地保护的研究

为快速识别配电网单相接地故障,断开故障线路并发出故障跳闸信号,仿真分析了配电网单相接地故障时故障线路和正常线路的暂态零序功率的特点,应用小波包精细分析配电网单相接地故障后的暂态零序功率,提取反映故障线路的暂态零序功率特征频带和信号窗长度;以零序电压作为单相接地保护的启动条件,以线路在特征频带和固定时间窗口的暂态零序能量为保护动作判据,构成配电网单相接地的反时限保护。仿真分析表明该单相接地保护动作原理不受短路时刻、接地电弧电阻、线路长度等因素的影响,满足继电保护"四性"要求。     

基于改进DTW的接地故障波形互相关度聚类选线方法

谐振接地系统发生单相接地故障时,各线路暂态零序电流波形具有非线性非平稳特性,故障线路与非故障线路的暂态零序电流波形存在差异性,提出一种基于改进动态时间弯曲距离(DTW)的接地故障波形互相关度聚类选线方法。通过改进DTW算法求取各线路发生故障后半个周期暂态零序电流波形两两之间的幅值互相关系数矩阵(ACCM),结合暂态零序电流极性互相关系数矩阵(PCCM),构造表征暂态零序电流幅值和极性信息的综合互相关系数矩阵(CCCM),由免阈值设定的模糊C均值聚类(FCM)算法选出故障线路。对噪声干扰、两点接地、电弧故障、采样不同步等情况的仿真结果表明,所提故障选线方法不受工程应用中可能存在的影响因素的影响,实现可靠选线。     

基于S变换相关度和深度学习的配电网单相接地故障选线新方法

针对配电网发生单相接地故障时特征信息不明显,且现有选线方法易受故障条件和环境噪声影响的问题,基于S变换相关度和深度学习,提出一种具有强抗噪声能力和高泛化水平的配电网单相接地故障选线新方法.首先,利用S变换获取零序电流时频信息,基于各线路零序电流的全频段信息计算线路故障信息相关度;其次,为提高故障特征的可辨识度和抗干扰性,提出一种S变换相关度图形(SCF)构建方法;在此基础上,建立含SCF层的卷积神经网络深度学习模型(S-CNN),并利用Simulink仿真模型生成的故障数据对其结构参数和超参数进行分步训练;最后,通过S-CNN提取配电网故障零序电流深层特征,实现故障选线,并测试了S-CNN在配电网不同运行状况和故障条件下的选线效果.仿真结果和实际配电网故障数据测试表明:在强噪声干扰场景中,基于S-CNN的故障选线模型在不同故障位置、故障相角、过渡电阻条件下可实现高正确率选线,且在各线路零序电流采样不同步条件下仍具有较强的鲁棒性.     

采用S变换相位差及能量相对熵的换流变零序差动保护新判据

针对换流变压器零序差动保护误动现象,提出一种采用S变换相位差及能量相对熵算法的换流变零序差动保护新判据。通过分析换流变压器区内各类故障、区外故障及外部故障切除时零序电流的特点,利用零序差动保护两侧自产零序电流和中性线上零序电流的相位和能量概率分布差异进行识别。当发生区外故障时,零序差动保护两侧零序电流的波形极为相似,其相位差和能量相对熵值都基本为0。当发生区内故障时,零序差动保护两侧零序电流相位相反且波形相似度小,其相位差接近180°且能量相对熵值增大。仿真验证表明,该判据可准确迅速识别区内与区外故障,其性能不受故障类型和过渡电阻的影响,且具有一定的抗电流互感器饱和的能力。