A Fault Feature Extraction Model in Synchronous Generator under Stator Inter-Turn Short Circuit Based on ACMD and DEO3S

This paper proposed a new diagnosis model for the stator inter-turn short circuit fault in synchronous generators.Different from the past methods focused on the current or voltage signals to diagnose the electrical fault,the sta-tor vibration signal analysis based on ACMD(adaptive chirp mode decomposition)and DEO3S(demodulation energy operator of symmetrical differencing)was adopted to extract the fault feature.Firstly,FT(Fourier trans-form)is applied to the vibration signal to obtain the instantaneous frequency,and PE(permutation entropy)is calculated to select the proper weighting coefficients.Then,the signal is decomposed by ACMD,with the instan-taneous frequency and weighting coefficient acquired in the former step to obtain the optimal mode.Finally,DEO3S is operated to get the envelope spectrum which is able to strengthen the characteristic frequencies of the stator inter-turn short circuit fault.The study on the simulating signal and the real experiment data indicates the effectiveness of the proposed method for the stator inter-turn short circuit fault in synchronous generators.In addition,the comparison with other methods shows the superiority of the proposed model.

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.

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.

变压器典型绕组缺陷的漏磁分布规律及编码辨识方法研究

针对目前变压器绕组缺陷时漏磁规律分析不全面、基于漏磁特征的绕组故障辨识研究不足的问题,该文以一台110kV变压器为原型,开展不同程度、不同位置、不同形式的绕组变形和匝间短路漏磁分布规律的有限元仿真研究,结果发现,无论是径向变形还是轴向变形,漏磁通分布规律受变形饼数影响较小,相同程度变形发生在高压绕组,绕组区域的漏磁通变化受形变位置影响较小,但低、中压绕组漏磁分布易受形变位置影响。端部绕组的变形更易引起漏磁变化。匝间短路引起的漏磁变化远大于绕组变形,并会额外影响油箱壁附近漏磁分布,同一位置匝间短路引起的漏磁变化分布情况受短路程度影响较小。此外,发生在低、中压绕组的匝间短路较高压绕组对漏磁分布的破坏程度更大。进一步地,该文提出一种基于漏磁变化量的绕组缺陷编码辨识方法,借助支持向量机法对不同程度同一缺陷下绕组附近5个漏磁监测点数据进行分类以确定阈值,将各处漏磁变化量根据阈值转化为对应的三进制数,最终形成一个十进制编码以实现对绕组变形和匝间短路缺陷的定位辨识。该方法的提出为变压器绕组故障提供了一种基于漏磁变化量的监测辨识手段,通过增加监测点、采用更高进制编码以细分阈值,该方法具备辨识不同程度缺陷的可能。相关成果已在110kV变压器上开展应用。

具有宽上阻带和双陷波的超宽带滤波器

基于偏置环形谐振器和加载电容器的缺陷地结构设计了一种具有宽上阻带和双陷波的超宽带滤波器。利用奇偶模分析法分析三阶接地短截线的传输极点与结构的对应关系,得到了一个具有五个传输极点的结构。通过采用三阶接地短截线结构和偏置环形谐振器的级联结构得到通带和宽上阻带,通带范围为2.95~12.24 GHz,相对带宽达到122%,上阻带大于10 dB,衰减范围至28.04 GHz。引入两个相同的H形缺陷地结构,并且在缝隙处焊接电容器,在2.69 GHz处共同产生传输零点来改善滤波器带外抑制特性。使用两个不同尺寸的半H形缺陷地结构分别在5.64 GHz和8.31 GHz处产生陷波,陷波衰减分别为16 dB和20 dB,提高滤波器的抗干扰能力。

Simplified mathematical model of inter-turn short circuit of field windings in hydro-generators and its application

Inter-turn short circuit of field windings is a common electrical fault of generators.Simulation is an important method of investigating the fault and providing data support for fault monitoring.However,huge numbers of pole pairs and damper loops in large hydro-generators would lead to lengthy calculation time,hindering scientific research and engineering application.To deal with this problem,we analyze a theoretical basis for a damper winding simplified model and then propose an equivalent treatment method.Through the analysis of steady-state current harmonic characteristics of generators with different stator winding configurations during the fault,the simplified models suitable for steady-state calculation are derived from two aspects,namely,additional rotor harmonic current frequency characteristics and the relationship of the amplitude as well as the phase of each branch current of the stator.The calculation and experimental results of the two simplified models are then compared to verify the models' correctness.A calculation example of the Three Gorges left bank VGS generator shows few deviations between the calculation results of the simplified model and the original model.Moreover,the calculation time using the simplified model is 1/1500 that using the original model,which provides a more effective tool for on-line fault monitoring.Finally,the sensitivity-verification application of the fault-monitoring scheme based on the stator steady-state unbalanced current RMS is depicted.The result shows that the scheme can monitor two-turn short circuits of field windings in the Three Gorges generator and provide high sensitivity.

Application of Morphological Max-Lifting Scheme for Identification of Induction Motor Stator Inter-turn Short Circuit

The harmonic components of stator winding current in induction motor will change under the condition of stator inter-turn short circuit.According to these characteristics,in this paper,a novel technique based on morphological maxlifting scheme is proposed for identification of induction motor stator inter-turn short circuit.A max-lifting scheme is applied to process stator winding currents to extract these characteristics.An indicator,r,is computed to identify the short circuit.The transient model of induction motor is employed to simulate oneturn to six-turn stator inter-turn short circuits in an induction motor.Extensive simulation work has been conducted under normal conditions,abnormal conditions(voltage imbalance and varying load),stator inter-turn short circuit conditions,and conditions of any combinations of the above.The results have shown that the scheme proposed in this paper has a high identification rate for induction motor stator inter-turn short circuit.

断路器分合闸线圈的绝缘缺陷与改进措施分析

为了研究断路器分合闸线圈的绝缘缺陷及特征,文中通过分析某断路器分合闸线圈的结构、电流、内部缺陷的原因及特征后发现,线圈缺陷的原因为线圈内部薄弱点在操作电流作用下产生局部过热或匝间短路;故障线圈不影响断路器的动作性能,但直流电阻下降,线圈电流增大,波形异常,返厂试验及解剖验证了分析的正确性。针对线圈的绝缘缺陷,文中最后提出了有效的防护措施并介绍了可有效发现缺陷线圈的脉冲检测法,实践证明,脉冲检测法明显提高了线圈的合格率。

一起220kV主变压器事故分析及处理

对一起变压器事故损坏情况进行了检查,对事故原因进行了分析,提出造成该次事故的原因是变压器低压引线的绝缘支架机械强度不够。为了避免类似事故的发生,变压器设计时不但要对绕组的抗短路能力进行验算,还应对引线支撑件的抗短路能力进行验算。

基于半残次硅片的太阳电池性能研究

选取了在硅片加工过程中产生的线痕片、厚片、薄片、崩片和TTV片共5种类型的半残次硅片,制备了太阳能电池,并在中山大学太阳能系统研究所进行了太阳电池片的实验研究,分析了这些残次片电池的开路电压、短路电流、填充因子、转换效率,研究结果表明,半残次硅片所制备的太阳电池性能良好:这些电池片的平均转换效率都达到了15.80%以上,填充因子可达73.98%,短路电流在5.10～5.28A之间,开路电压在0.62V以上,对于降低太阳电池成本具有一定参考价值.

短接小径管的漏磁检测

建立了小径管缺陷漏磁检测的三维有限元模型,得到缺陷漏磁场的空间分布特性。通过改变缺陷的深度和宽度,研究了腐蚀缺陷对漏磁检测信号的影响,研发了短接小径管的漏磁检测装置,在规格(外径×壁厚)为Ф27mm×3.5mm小径管内壁加工了人工腐蚀坑缺陷,并对模拟缺陷进行检测。结果表明:漏磁检测技术可以实现短接小径管腐蚀缺陷的快速扫描检测。

SMT焊接常见缺陷及解决办法

对采用SMT生产的印制电路组件中出现的几种常见焊接缺陷现象进行了分析,并总结了一些有效的解决措施。

电子装联过程中常见焊接缺陷及解决办法

在电子装联过程中会不可避免地出现焊接缺陷。文章结合作者工作中的体会和经验,对采用SMT生产的印制电路组件中出现的几种常见焊接缺陷现象进行了分析,并总结了一些行之有效的解决措施,希望能对相关技术人员有所帮助。

基于频域特性的玻璃过孔缺陷无损检测方法

玻璃通孔(Through glass vias,TGV)因玻璃衬底损耗较低,成为一种比硅通孔(Through silicon vias,TSV)传输性能更优的三维集成电路技术,备受瞩目.而TGV加工过程中因精度不理想,热失配,过孔倾斜等原因易造成短路、开路等缺陷.因此,需要有效的无损检测技术来提升产品收率.本文通过分析地-信号-信号-地(Ground-signal-signal-ground,GSSG)型玻璃过孔的频域传输特性及耦合特性,提炼出无损检测缺陷的方法.即根据S参数及|S21|和|S11|之差的特点,判断传输通道是否出现开路或短路缺陷;此外,还探索出当短路、开路缺陷同时出现时,判断缺陷相对位置的方法.最后探讨了如何利用|S11|和|S31|来定位开路点和短路点.为TGV的无损检测提供了一种有效、简便的方法.

基于DCS系统数据驱动的汽轮发电机转子绕组匝间短路缺陷检测

本文提出一种基于分散控制系统(Distributed Control System,DCS)实时监测数据驱动的汽轮发电机转子绕组匝间短路缺陷检测方法。首先,建立基于滑动窗口的稀疏自编码器(Sparse Auto Encoder,SAE)模型,对汽轮发电机组正常运行状态下所获取的DCS实时监测数据进行稀疏重构以提取状态特征;其次,建立基于注意力机制优化的长短期记忆网络(LSTM)模型以预测正常工况下汽轮发电机的励磁电流;最后,通过计算励磁电流理论预测值与实际值的残差对转子绕组匝间短路缺陷进行预警。安徽某电厂600MW大型汽轮发电机DCS历史监测数据分析结果表明该方法能够及时识别汽轮发电机转子绕组匝间短路的早期缺陷。

VLSI电路短路和开路故障模型研究进展

本文概述了近十年来VLSI电路的短路和开路缺陷及其故障建模的研究进展。本文将VLSI电路短路缺陷分为逻辑门内部的短路和逻辑门之间的互连短路两大类,重点介绍了栅氧短路和桥接故障模型。相应地,文中将 VLSI电路的开路缺陷分为逻辑门内部的开路和逻辑门之间的互连开路两大类,重点介绍了逻辑门内部的网络断开、浮栅和互连开路的故障模型。文中还讨论了故障模型与测试的关系。分析结果表明,目前已有的短路和开路故障模型还不够完善,特别需要研究故障机制对电路中其它节点动态行为的依赖性和对噪声的敏感性。

超宽带微带带通滤波器的设计

为了设计小型化、低插入损耗、宽阻带的滤波器,本文基于缺陷微带结构(defected microstrip structure,DMS)提出一种新型H形DMS结构微带滤波器,利用DMS结构与1/4波长终端短路谐振器设计制作一种小型超宽带微带带通滤波器,并用ADS(advanced design system)软件对该滤波器进行分析及仿真验证,且对所设计的滤波器进行实物加工测试。测试结果表明,该滤波器的相对带宽达到了116%,阻带在-20dB以下的频段为12~19GHz,其宽度达到了7GHz,与理论分析基本一致。该滤波器尺寸为13.7mm×6.8mm,同时还具有插入损耗小、结构简单紧凑等优点。

基于输入阻抗谱的电力电缆缺陷和故障特征研究

分析了城市电网建设中电力电缆缺陷和故障类型的特征,提出了一种电缆首端输入阻抗谱特征的研究方法,搭建了不同缺陷和故障类型的电缆仿真模型,并与实际测试结果进行了对比分析。结果表明:电缆缺陷会引起输入阻抗谱的偏移和谐振频率点的变化;开路故障和短路故障会增大输入阻抗谱的振荡周期;仿真曲线和测试结果基本一致。

变压器阻抗保护缺陷的分析

针对变压器阻抗保护的保护范围进行分析 ,指出了变压器阻抗保护的缺陷 ,同时指出线路距离保护不能作为对侧主变压器的后备保护。

220kV变电站GIS断路器短路典型事故分析

介绍了某220 kV变电站气体绝缘金属封闭开关设备(gas insulated metal enclose switchgear,GIS)断路器短路事故经过。通过对220 kVGIS短路事故后的故障录波、气体成分、断路器解体及出厂原始数据的综合分析,认为在出厂时的雷电冲击试验中的击穿、放电造成的断路器极间绝缘筒的缺陷是事故发生的主要原因。并通过事故过程的还原从另一角度验证了事故原因分析的正确性,并提出了相应的建议,同时为类似GIS故障的处理分析提供借鉴与参考。