Fault Diagnosis Based on ANN for Turn-to-Turn Short Circuit of Synchronous Generator Rotor Windings

Rotor winding turn-to-turn short circuit is a common electrical fault in steam turbines. When turn-to-turn short circuit fault happens to rotor winding of the generator, the generator terminal parameters will change. According to these parameters, the conditions of the rotor winding can be reflected. However, it is hard to express the relations between fault information and generator terminal parameters in accurate mathematical formula. The satisfactory results in fault diagnosis can be obtained by the application of neural network. In general, the information about the severity level of the generator faults can be acquired directly when the faulty samples are found in the training samples of neural network. However, the faulty samples are difficult to acquire in practice. In this paper, the relations among active power, reactive power and excitation current are discovered by analyzing the generator mmf with terminal voltage constant. Depending on these relations, a novel diagnosis method of generator rotor winding turn-to-turn short circuit fault is proposed by using ANN method to obtain the fault samples directly, without destructive tests.

A fault warning for inter-turn short circuit of excitation winding of synchronous generator based on GRU-CNN

Synchronous generators are important components of power systems and are necessary to maintain its normal and stable operation.To perform the fault diagnosis of mild inter-turn short circuit in the excitation winding of a synchronous generator,a gate recurrent unit-convolutional neural network(GRU-CNN)model whose structural parameters were determined by improved particle swarm optimization(IPSO)is proposed.The outputs of the model are the excitation current and reactive power.The total offset distance,which is the fusion of the offset distance of the excitation current and offset distance of the reactive power,was selected as the fault judgment criterion.The fusion weights of the excitation current and reactive power were determined using the anti-entropy weighting method.The fault-warning threshold and fault-warning ratio were set according to the normal total offset distance,and the fault warning time was set according to the actual situation.The fault-warning time and fault-warning ratio were used to avoid misdiagnosis.The proposed method was verified experimentally.

Analysis on the fault characteristics of three-phase short-circuit for half-wavelength AC transmission lines

Half-wavelength AC transmission(HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the construction and operation of HWACT to analyze its fault features and corresponding protection technology. In this paper, the steady-state voltage and current characteristics of the bus bar and fault point and the steady-state overvoltage distribution along the line will be analyzed when a three-phase symmetrical short-circuit fault occurs on an HWACT line. On this basis, the threephase fault characteristics for longer transmission lines are also studied.

The simulation research for transient current variation in short circuit fault of urban rail transportation

Urban rail transit is one of the most important way for urban residents. However, frequent power failure, especially the short fault hinders the safe and stable operation of rail transit. The research of the transient variation of line electrical parameters in short circuit fault is the basis of researches for technology of line protection and short circuit fault location. Based on Matlab/Simulink, a 24-pulse rectifier circuit model is established, the resistance and inductance value of the catenary and rail network are calculated. The short Circuit fault simulation model of DC traction power supply system is established. The short-circuit fault of the traction network at close and distant points are simulated, the transient variation values of fault current with the different fault distance are analyzed. The simulation results show that the transient current peak of the nearby short circuit is oscillatory and convergent due to the nonlinear devices, which proves the accuracy of the model and provides a reference for the precise configuration of the line protection equipment.

fault500 kV变电站35 kV串联电抗器故障分析及建议

某500kV变电站主变35kV侧发生一起电容器组串联电抗器短路故障,通过对事故现场检查,结合故障录波器记录,对本次事故发生的过程进行了分析并得出结论。针对本次故障暴露出的问题,从串联电抗器安装位置、在线监测等方面提出了事故防范措施,对于变电站电容器组安全运行具有一定参考价值。

The Detection of Inter-Turn Short Circuits in the Stator Windings of Sensorless Operating Induction Motors

This work proposes an alternative strategy to the use of a speed sensor in the implementation of active and reactive power based model reference adaptive system (PQ-MRAS) estimator in order to calculate the rotor and stator resistances of an induction motor (IM) and the use of these parameters for the detection of inter-turn short circuits (ITSC) faults in the stator of this motor. The rotor and stator resistance estimation part of the IM is performed by the PQ-MRAS method in which the rotor angular velocity is reconstructed from the interconnected high gain observer (IHGO). The ITSC fault detection part is done by the derivation of stator resistance estimated by the PQ-MRAS estimator. In addition to the speed sensorless detection of ITSC faults of the IM, an approach to determine the number of shorted turns based on the difference between the phase current of the healthy and faulty machine is proposed. Simulation results obtained from the MATLAB/Simulink platform have shown that the PQ-MRAS estimator using an interconnected high-gain observer gives very similar results to those using the speed sensor. The estimation errors in the cases of speed variation and load torque are almost identical. Variations in stator and rotor resistances influence the performance of the observer and lead to poor estimation of the rotor resistance. The results of ITSC fault detection using IHGO are very similar to the results in the literature using the same diagnostic approach with a speed sensor.

Short-circuit Current Characteristics of Wind Generators

To study the effects of wind generators on distribution system protection,the short-circuit current(SCC) characteristics of wind generators is important.Although there are many researches on the issue,a clear agreement has not been reached so far.The SCC characteristics for different wind generators are studied.PSCAD simulation is performed in the same system integrated with different kinds of wind generators,and their results are compared with those reported in IEEE papers.The detection possibility by overcurrent relay(OCR)is discussed based on the simulation results.

Reducing the Short Circuit Levels in Kuwait Transmission Network

This paper describes the study analysis performed to evaluate the available and potential solutions to control the highly increasing short circuit （SC） levels in Kuwait power system. The real Kuwait High Voltage （HV） network was simulated to examine different measures at both 275 kV and 132 kV stations. The simulation results show that the short circuit currents exceed the permissible levels （40 kA in the 132 kV network and 63 kA in the 275 kV network） in some specific points. The examined measures include the a study on changing the neutral point policy, changing some lines from alternating current （AC） to direct current （DC）, dividing specific bus bars in some generating stations and applying current limiters. The paper also presents a new plan for the transmission network in order to manage the expected increase in short circuit levels in the future.

基于阻抗在线测量的锂离子电池过放电诱发内短路识别研究

锂离子电池的过放电行为可诱发内短路进而可能导致热失控。由于单体电池一致性差异和过放电导致的内短路初期电、热特征不明显,使得电压和温度等常规物理参数难以可靠实现故障预警,而阻抗可以反映电池内部信息,对故障状态具有较好的指示能力。该文通过分析锂离子电池过放电诱发内短路引起阻抗变化的机理,基于设计的阻抗在线测量装置,确定用于监测电池内短路故障的特征阻抗频率为70 Hz,获取过放电诱发内短路过程中特征频率下动态阻抗及阻抗变化率,提出一种基于动态阻抗特征的内短路在线识别方法并验证了方法的可靠性。实验结果表明,锂离子电池放电过程中动态阻抗半正弦变化特征可提前约144 s实现过放电预警,动态阻抗针状变化特征可提前约152 s实现内短路故障预警,动态阻抗明显回升特征可作为内短路发生的标志。此外,阻抗变化率特征有助于实现锂离子电池故障识别及预警,该方法在锂离子电池故障在线快速诊断中具有重要的应用潜力。

多间隔信息融合的母线保护电流互感器断线再开放策略

对于电流互感器(CT)断线后发生金属性故障的情景,现有母线保护采取的闭锁差动保护动作方式将会引发多个变电站停电。此外,当母线区内发生高阻接地故障时,现有母线保护判据可能会将其误判为CT断线故障,不利于电力系统的安全稳定运行。针对这一问题,提出了一种母线保护CT断线再开放策略,该策略基于断线间隔与非断线间隔的零序电流变化量对负荷波动和故障进行区分,并基于非断线间隔的差流有效值和间隔失灵保护信息对区内外故障进行判别。实时数字仿真系统仿真结果验证了所提CT断线识别判据和再开放策略的正确性。

基于累积和事件段识别与改进谱聚类的锂离子电池储能系统内短路故障检测方法

锂离子电池系统的内短路故障可能导致严重安全事故,其检测受到在线检测实时性以及故障特征获得性制约,是当下锂离子电池储能系统安全运行亟待解决的问题。该文提出一种基于累积和(cumulative sum,CUSUM)事件段检测与改进谱聚类的锂离子电池储能系统内短路故障检测方法。首先,考虑内短路故障时的电压/温度变化特性,基于累积和事件突变点识别方法,识别疑似内短路故障事件段。其次,构建三维故障特征,刻画检测对象内短路故障特征属性。然后,构建基于Wasserstein测度的内短路故障特征距离矩阵,检测三维空间各点稀疏特性,客观划定故障聚类,实现内短路故障检测。搭建锂离子电池内短路实验平台、建立锂离子电池电–热耦合仿真模型,算例结果表明该文方法能够准确识别疑似内短路故障事件段,在不同串并联形式及故障类型下实现故障检测,证明了该文方法的正确性与可行性。

基于短时傅里叶变换和深度网络的模块化多电平换流器子模块IGBT开路故障诊断

针对现有模块化多电平换流器(MMC)子模块故障诊断过程中所需传感器较多、测量干扰较大等问题,提出一种基于深度学习的MMC子模块IGBT开路故障诊断方法。在对MMC子模块开路故障特征进行分析的基础上,利用短时傅里叶变换(STFT)提取桥臂电压信号的谐波分量信息作为故障诊断所需的特征参数。将所得到的特征参数进行处理后构建故障诊断样本,在通过深度置信网络实现故障类型快速检测的基础上,依据不同故障类型,构建多个基于卷积神经网络的故障定位网络,进而实现开路故障的检测与定位。通过129电平的MMC系统仿真模型和降功率的MMC实验系统搭建,对该文所提方法进行了验证。仿真和实验结果表明,所提故障诊断方法可以在减少传感器数量的基础上实现子模块开路故障的诊断,提高系统的可靠性。

基于FFT-LSTM的抽水蓄能发电机定子匝间短路故障诊断方法

定子短路故障是抽水蓄能发电机常见的故障之一,其会对发电机的性能和安全性产生严重影响,为确保抽水蓄能发电机安全稳定运行,提出基于FFT-LSTM的抽水蓄能发电机定子短路故障诊断方法。建立抽水蓄能发电机定子绕组匝间短路故障模型,分析定子绕组匝间短路故障时,发电机定子电、磁相关状态。以抽水蓄能发电机定子绕组匝间短路故障时的三相电流信号为依据,基于磁势相等原理将三相电流变换成两相电流后,利用FFT转换定子两相电流的时域信号为频域信号,获取故障电流频谱图输入LSTM网络中进行处理,输出抽水蓄能发电机定子绕组匝间短路故障诊断结果。实验结果表明,该方法可以更好地区分抽水蓄能发电机正常与故障状态,实现抽水蓄能发电机定子绕组匝间短路故障诊断,且故障诊断的交叉熵损失低。

基于相位差的轴向磁通无铁心电机早期轻微匝间短路故障诊断

针对轴向磁通定子无铁心电机早期匝间短路故障问题,提出一种基于零序分量和定子电流分量相位差的轴向磁通定子无铁心电机的早期匝间短路故障诊断和定位方法。首先,根据定子绕组电感极小的特点建立了匝间短路故障数学模型;其次,对故障前后的短路电流、相电流、零序分量等进行了傅里叶分析,通过零序电压基波幅值变化对匝间短路故障进行识别;最后,通过对比零序电压基波与定子三相电流初相位差来进行故障相定位。结果表明,匝间短路故障相的相电流基波初始相位与零序电压基波初相位差的绝对值近似180°,而健康相的相位差与180°相差较大。基于相位差可以实现轴向磁通无铁心电机早期匝间短路故障的诊断与定位,为永磁电机的匝间短路故障诊断提供了参考。

不对称短路故障下永磁直驱风电机组并网控制策略研究

电网侧发生不对称故障时,永磁直驱风电机组并网电流会发生三相不平衡的问题。针对这一问题,提出一种基于自适应陷波器的网侧换流器控制策略。该控制策略基于解决机组并网电流二倍频分量的思想,在电网侧发生不对称短路故障时,将进入逆变器的dq坐标系下的二倍频电压分量去除,从而使得网侧换流器输出的电流达到三相平衡。本文首先分析了电网侧发生不对称短路故障后永磁直驱风力发电机组的动态响应;然后建立了机侧和网侧换流器的模型,并分别采用了双闭环矢量控制技术和基于自适应陷波器的控制策略;最后进行仿真分析,验证了改进后的控制策略相较于传统控制策略,有效解决了不对称短路故障下并网电流三相不平衡问题。

不同容量下并网模式交流微电网短路故障早期检测与区域定位

随着分布式电源(distributed generation,DG)的容量变化,微电网原有的供电结构发生改变,使得潮流大小、方向和功率结构发生变化,对快速检测和定位微电网中的短路故障区域提出了挑战。在MATLAB/Simulink中搭建低压交流微电网模型;通过高尺度小波能量谱算法对微电网与大电网公共连接点(point of common coupling,PCC)处检测到的电流进行分解,提取适应不同容量情况的短路故障特征值,实现了不同容量下微电网短路故障的早期检测;利用小波能量谱特征结合基于正交最小二乘法(orthogonal least square,OLS)的径向基函数(radial basis function,RBF)神经网络算法提出一种适用于不同容量微电网的短路故障区域定位方法,并进行仿真验证;在此基础上设计并网模式微电网短路故障保护硬件系统,并进行实验验证。结果表明,所设计的保护系统能够快速、准确地同时实现并网模式下交流微电网短路故障的早期检测与区域定位。

基于扰动观测器的五相永磁同步电机开路和短路容错矢量控制

针对反电动势含有3次谐波的五相永磁同步电机(PMSM)开路和短路故障导致转矩脉动大的问题,该文提出一种基于扰动观测器的矢量控制(DOB-FOC)策略。该策略基于降阶正交变换矩阵在同步旋转坐标系上建立PMSM开路故障情况下的基波模型,将3次谐波反电动势、短路电流等作为扰动信号。在此基础上,设计扰动观测器,观测出以上扰动导致的转矩脉动,将其转化为q轴补偿电流前馈到q轴电流指令中,有效地抑制了故障导致的转矩脉动,并且实现了PMSM在开路和短路故障情况下的平稳无扰运行。仿真和实验结果验证了所提容错策略的有效性。

逆变型电源场站故障稳态电流实用化计算方法

单机倍乘法常用于逆变型电源场站的故障稳态建模,可简单估算场站短路电流水平,但计算精度有待提升。文中首先分析了低电压穿越控制策略约束下,有功出力、电压跌落程度对发电单元输出的稳态电流的决定性作用,得出故障稳态电流输出特性曲线,基于此分析了场站电气距离及有功出力差异对单机倍乘法计算误差的影响。在误差分析的基础上,提出了计及发电单元分布特性的改进单机倍乘法。该方法在发电单元接入点电压计算中,利用等值阻抗来等效发电单元与并网点的电气距离;将场站分群等值为两台机组,减小发电单元间有功出力差异对短路特性的影响。不同场景下的仿真分析表明,改进方法计算精度较单机倍乘法有着较大的提升。所提方法仅需通过简单计算即可实现场站分群和短路电流聚合,有较好的工程实用性。

永磁同步电机故障诊断方法研究综述

永磁同步电机(permanent magnet synchronous motor,PMSM)具有结构简单、运行稳定、效率高和外形多样等显著优点,在生产制造领域得到广泛应用。PMSM在工作中不断受到速度变化和负载波动等复杂工况的影响,不可避免地会出现各种故障,如轴承故障、偏心故障、退磁故障和匝间短路故障等。文中综述了PMSM常见故障类型,并总结了自动化领域中基于信号的状态监测方法的现有研究,以用于各类电气和机械故障的检测和诊断。随后,对诊断方法进行了总结,并分析了其优势与限制,探讨了不同信号处理方法在应用中的利弊。最后,根据当前研究现状,讨论了PMSM故障监测与诊断存在的问题和未来发展方向。

新型同步调相机匝间短路故障机理分析

随着新型同步调相机大规模投入运行,调相机的安全问题逐渐凸显。绕组匝间短路故障是调相机1种典型故障,对调相机长期运行和电网稳定都有严重影响。该文从两种故障发生后对气隙磁场磁动势的影响出发,建立转子总电流、定子绕组相电流、支路电流及电磁转矩的统一数学表征,从幅值、相位、谐波含量等多方面对两种故障进行深入的对比分析,揭示新型同步调相机绕组匝间短路故障机理。该文基于已投入使用的TTS-300-2型新型同步调相机,开发有限元软件的仿真程序,搭建调相机模拟机的实验平台。理论分析结果分别得到了仿真与实验结果的验证。