Diagnosis of Short‐Circuit Faults in Stator Winding Inside Low‐Voltage Induction Motor Using Impulse Voltage Test

Short‐circuit faults in windings due to the deterioration of insulation is among the most common faults in motor drive systems. An easy and effective fault diagnosis method is urgently required to ensure highly reliable operation. This paper proposes a novel method for the diagnosis of short‐circuit faults in stator winding inside a low‐voltage induction motor without removing the rotor, by performing an impulse voltage test. As the rotor does not need to be removed from the motor in this novel diagnosis method, the method can be put to practical use. In this study, first, several impulse voltage tests are carried out on the stator windings of motors. Second, the values of two features that represent the characteristics corresponding to the condition of the motor are calculated, and it is found that the shape of the feature distribution does not depend on the rotor position but on the condition of the winding. Third, the distance between the feature distribution for the healthy motor and features obtained from a target motor is calculated. On the basis of this distance, the condition of the stator winding inside the induction motor is determined. The effectiveness of the proposed diagnosis method is verified by performing experiments that involve several motors with healthy and faulty windings.     

水内冷汽轮发电机定子端部绕组绝缘故障检测手段探讨

介绍了某电厂１台１００ＭＷ水内冷汽轮发电机定子绕组事故简况,分析和研究了如何改进目前大修时所采取的检测手段以及确保及时发现定子端部绕组缺陷的方法,并对检修工作提出了几点建议。     

双馈异步发电机定转子绕组过热故障监测方法

双馈异步发电机(DFIG)在长期运行中很容易发生定转子绕组过热故障。以绕组温度为研究对象,在分析绕组过热故障成因的基础上,分别从电机热性能和参数辨识两方面进行检测。使用参数辨识法时,首先利用电机电磁数学模型辨识定转子绕组电阻,再根据电阻与温度之间的关系计算定转子温度,从而判断绕组是否过热。最后基于MATLAB软件仿真验证了定转子绕组参数辨识法的正确性,为DFIG诊断绕组过热故障提供理论支撑。     

Online temperature monitoring of a grid connected induction motor

This paper proposes a novel method for continuous temperature measurement of the stator winding of an induction machine. The method is based on measuring stator winding resistance by injecting a DC current test signal into the motor neutral point without interrupting its normal operation. The entire stator winding is used as a sensor without additional thermal sensors, while DC voltage and current need to be measured solely. Virtually equal currents are injected in each phase thereby minimizing the influence on the motor torque inherent to contemporary signal injection-based methods. The measurement results obtained using the proposed method are compared to results obtained using the standard resistance-based method and direct measurements obtained from thermocouples embedded in the windings. An excellent match is achieved under various loading levels and variable cooling conditions, thus proving the accuracy and robustness of the proposed method.     

基于FFT-LSTM的变速抽蓄机组转子绕组短路故障和偏心故障诊断方法

变速抽水蓄能机组是适应系统功率波动的重要调节手段。转子绕组短路故障和转子偏心故障是其常见的故障类型,两种故障均会在定子侧感应生成特征频带相近的谐波环流,导致两种故障难以被区分。提出了一种基于快速傅里叶变换-长短期记忆(fast Fourier transform-long short-term memory, FFT-LSTM)网络的故障诊断方法,以细化分辨故障特征相近的转子绕组短路故障和转子偏心故障。所提方法以定子分支环流的谐波分量为特征量进行故障诊断,分别推导了两种故障发生时定子侧环流谐波特征,并总结二者间的相似性和差异性。鉴于该差异较为微弱,引入长短期记忆(longshort-termmemory, LSTM)神经网络算法对其进行辨识。利用内部故障仿真模型对可能发生的转子绕组短路故障和偏心故障进行批量仿真,以得到用于LSTM网络训练和测试的数据集。仿真结果表明FFT-LSTM能够准确诊断不同转速下变速抽蓄机组的转子绕组短路故障和转子偏心故障。     

Double Three-phase Induction Machine Modeling for Internal Faults Simulation

Multi-phase induction motors present excellent characteristics for faulty tolerant operation. Among them, six-phase induction motors, which are among the most used, exhibit two types of configuration: the double three-phase and the six-phase with single neutral. The double three-phase presents the advantage of reducing harmonics with its symmetric winding. This article presents a new modeling of the double three-phase induction machine for internal faults simulation. The developed model is composed by two sets of three-phase stator windings forming two stars. The model considers an arbitrary displacement (α) between stator stars, allowing the simulation of this type induction machines with different configurations, with 60° displacement used herein. The simulations of internal faults, such as stator windings or rotor faults, are both considered in the proposed model, allowing the machine study under abnormal conditions. The double three-phase induction machine model was fully implemented in real coordinates, making it possible to simulate stator and rotor faults without being necessary to change system equations coordinate. Several examples allow verifying the characteristics of the proposed model and its application for internal fault analysis. Experimental results are also presented to validate the obtained simulation results.     

凸极发电机绕组故障瞬变过程仿真的支路分解组合法

以工程应用为背景,研究多分支绕组大型水轮发电机定子绕组故障瞬变过程的数值仿真方法。定子绕组发生故障后,绕组对称性遭到破坏,传统的变换方法难以应用;若按各支路列写方程,则方程维数过高,而且收敛也比较困难。本文提出支路分解组合法,以独立支路计算参数;同时归并健全分支,降低方程维数,进而建立完整的数学模型。测试结果表明,用该方法研究快速继电保护特性及现场事故分析能够满足工程要求。     

十五相感应电机一相开路时的稳态特性

根据十五相感应电机的稳态数学模型和稳态的对称分量法,对十五相感应电机在一相开路时的稳态特性进行分析,结果表明一相开路时,剩余各相定子电流均有所增加,平均转矩没有明显变化,实验结果验证了上述结论,该方法可推广到多相定子绕组开路情形.     

A new digital ground-fault protection system for generator–transformer unit

Ground faults are one of most often reasons of damages in stator windings of large generators. Under certain conditions, as a result of ground-fault protection systems maloperation, ground faults convert into high-current faults, causing severe failures in power system. Numerous publications in renowned journals and magazines testify about ground-fault matter importance and problems reported by exploitators confirm opinions, that some issues concerning ground-fault protection of large generators have not been solved yet or have been solved insufficiently. In this paper a new conception of a digital ground-fault protection system for stator winding of large generator was proposed. The process of intermittent arc ground fault in stator winding has been briefly discussed and actual ground-fault voltage waveforms were presented. A new relaying algorithm, based on third harmonic voltage measurement was also drawn and the methods of its implementation and testing were described.     

水轮发电机定子绕组绝缘击穿原因分析及处理

由于万家寨水电站4号水轮发电机定子铁心硅钢片溢出划破线棒绝缘,导致进行定子绕组交流耐压试验(大修前)时绝缘击穿造成接地故障,通过"直流高压放电方法"进行接地点检查,最后将所有线棒拔出进行检查、修复或更换,故障得以消除。     

Detection of stator short circuit faults in three-phase induction motors using motor current zero crossing instants

Stator faults typically have a significant share amongst the common type of faults in industrial three-phase induction (asynchronous) motors. This paper presents a motor current signature analysis (MCSA)-based diagnostics of the stator winding short circuit fault. This type of fault happens due to the destruction of the turn insulation, and can be very detrimental causing motor shutdown. Instead of traditional MCSA using the motor stator current, in this paper, analysis using the zero crossing time (ZCT) signal of the stator current is presented. The theoretical aspects of the stator short circuit detection are presented. Following that, a diagnostic algorithm utilizing the ZCT signals is proposed. Experiments are performed with real motors, healthy and with shorted stator windings. Frequency analysis of the ZCT signals from the experimental data substantiates the theoretical arguments with significant accuracy.     

大型凸极同步发电机定子绕组内部故障瞬态仿真

大型凸极同步发电机定子绕组内部故障的仿真计算对保护的配置具有重要意义。文中以多回路理论为依据，建立了大型凸极同步发电机定子绕组内部故障瞬态分析的数学模型；以匝间短路为例，给出了系数变化矩阵。通过在动模机上进行故障的动态模拟实验，验证了该方法的正确性。最后对三峡电站SF700－80／19720大型水轮发电机定子绕组一支路发生匝间短路的故障情况，进行了瞬态过程的仿真计算，验证了所配置单元件横差保护的灵敏度，结果令人满意。     

海上双馈感应发电机定子绕组匝间短路容错技术可行性分析

受海洋恶劣环境影响,海上双馈感应发电机(DFIG)定子绕组匝间短路故障频发,伴随海上可及性差引起的故障维修困难、停运损失巨大,使得容错技术需求日趋迫切。文中根据DFIG定子绕组匝间短路故障特点,构建精确通用的定子绕组匝间短路模型。针对故障后定子电流负序分量幅值增大而严重影响DFIG正常运行的问题,分离各序分量并提取定子负序电流,通过在转子侧输入相应的谐波电压来抵消定子侧负序电流,构建负序电流控制器以抑制故障后定子相电流的负序分量。仿真与实验结果验证了该方法可以有效降低DFIG定子绕组匝间短路故障后的定子负序电流幅值与输出功率脉动。     

基于定子线圈探测的转子匝间短路故障识别方法

该文通过对汽轮发电机转子线圈匝间短路时的电磁特性进行分析和计算，提出转子绕组匝间短路时，转子绕组主磁场变化比漏磁场明显，用定子线圈作为探测故障线圈，确立了转子绕组匝间短路故障程度和有效磁场损失之间的对应关系：提出转子匝间短路导致发电机定子绕组并联支路之间出现了电势差和环流，其大小和分布与短路严重程度有一定对应关系；利用动模试验机组进行了有关的验证，试验结果和理论推导相吻合。     

一种适用于谐波起动电动机的新型定子绕组

通过对谐波起动电动机广泛采用的定子绕组存在问题的分析,提出了一种结构更加简单、控制更加方便的定子绕组,该定子绕组线圈的匝数、线规都相同,解决了谐波起动电动机定子绕组不等匝引起的设计和制造工艺困难的问题.对该绕组的设计方法进行了分析和介绍,并以8极72槽定子绕组实例加以说明.     

A novel protection scheme for synchronous generator stator windings based on SVM

This paper proposes a novel scheme for detecting and classifying faults in stator windings of a synchronous generator (SG). The proposed scheme employs a new method for fault detection and classification based on Support Vector Machine (SVM). Two SVM classifiers are proposed. SVM1 is used to identify the fault occurrence in the system and SVM2 is used to determine whether the fault, if any, is internal or external. In this method, the detection and classification of faults are not affected by the fault type and location, pre-fault power, fault resistance or fault inception time. The proposed method increases the ability of detecting the ground faults near the neutral terminal of the stator windings for generators with high impedance grounding neutral point. The proposed scheme is compared with ANN-based method and gives faster response and better reliability for fault classification.     

HARMONIC ANALYSIS OF INDUCTION MOTORS WITH STATOR FAULTS

ABSTRACT

In the paper stator faults are analyzed by means of a procedure based on the space-vector theory. The used approach, due to Stepina, allows to consider separately each conductor of every single slot and therefore to take easily into account the winding dissymmetry.

The interactions among the different harmonic fields are studied by starting from the topological structure of windings and the harmonic analysis of the currents and of torque Is carried out.

The method is tested to numerical computations of steady-state currents for an induction machine with different positions of stator short-circuits.

Finally the procedure is validated by using an experimental squirrel cage machine, having stator windings constructed so as to realize different short-circuits.     

A novel protection scheme for synchronousgenerator stator windings based on SVM

Integration of electric vehicles (EVs), demand response and renewable energy will bring multiple opportunities for low carbon power system. A promising integration will be EV battery swapping station (BSS) bundled with PV (photovoltaic) power. Optimizing the configuration and operation of BSS is the key problem to maximize benefit of this integration. The main objective of this paper is to solve infrastructure configuration of BSS. The principle challenge of such an objective is to enhance the swapping ability and save corresponding investment and operation cost under uncertainties of PV generation and swapping demand. Consequently this paper mainly concentrates on combining operation optimization with optimal investment strategies for BSS considering multiscenarios PV power generation and swapping demand. A stochastic programming model is developed by using state flow method to express different states of batteries and its objective is to maximize the station’s net profit. The model is formulated as a mixed-integer linear program to guarantee the efficiency and stability of the optimization. Case studies validate the effectiveness of the proposed approach and demonstrate that ignoring the uncertainties of PV generation and swapping demand may lead to an inappropriate batteries, chargers and swapping robots configuration for BSS.     

变频电动机耦合电容分析与计算研究

脉宽调制(PWM)变频驱动器在提高交流传动系统效率的同时,产生的高次谐波导致共模电流显著增加。其中电动机定子绕组与定子铁心之间的耦合电容是共模电流的主要通路。准确计算定子绕组与定子铁心之间的耦合电容对于预测共模电流具有重要意义。由于电机绕组内部导线排列不规则,准确进行解析计算较为困难,将其简化为集中导体后,会导致计算精度变差。在绕组全散线模型的基础上,提出了一种简化散线建模方法,能在计算精度不变的情况下,有效地减小模型的复杂度。通过对比解析计算、全散线模型、简化散线模型和测量值,验证了该方法的有效性。     

大型汽轮发电机定子绕组端部状态评估及综合治理方法

模态试验分析是发电机定子绕组端部结构状态评估的主要方法,已广泛应用于大型发电机检修中.基于发电机定子端部绕组动特性解析与模态参数统计分析,提出了定子绕组端部椭圆型固有频率的适宜范围,确定了优秀、良好、合格对应具体频率区间,形成了定子端部绕组分级评价方法及故障诊断流程,在此基础上给出了现场定子绕组刚度和质量的模态频率调整...