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.

Electromagnetic Performance Prediction for the Symmetrical Dual Three-phase Surface-mounted PMSM under Open-phase Faults Based on Accurate Subdomain Model

The paper presents an accurate analytical subdomain model for predicting the electromagnetic performance in the symmetrical dual three-phase surface-mounted permanent magnet synchronous machine(PMSM)under open-phase faulty conditions.The model derivations are extended from previous accurate subdomain models accounting for slotting effects.Compared with most conventional subdomain models for traditional three-phase machines with nonoverlapping winding arrangement,the subdomain model proposed in this paper applied for the 24-slot/4-pole dual three-phase machine with symmetrical overlapping winding arrangement.In order to investigate the postfault electromagnetic performance,the reconfigured phase currents and then current density distribution in stator slots under different open-circuit conditions are discussed.According to the developed model and postfault current density distribution,the steady-state electromagnetic performance,such as the electromagnetic torque and unbalanced magnetic force,under open-circuit faulty conditions are obtained.For validation purposes,finite element analysis(FEA)is employed to validate the analytical results.The result indicate that the postfault electromagnet performance can be accurately predicted by the proposed subdomain model,which is in good agreement with FEA results.

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 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.

The Influence of Thrust Fault Structure on Cross-fault Short-leveling Survey

Aiming at different variation patterns of cross-fault short-leveling before earthquakes,the paper establishes the 2-D finite-element models with different crustal stratification and fault occurrence perpendicular to Longmenshan fault zone. By contact analysis and viscoelastic finite element method,the influence of fault structure on cross-fault short-leveling is obtained under the same constraint conditions,the results show that:with the increase of the horizontal projection distance of fault,the cumulative displacements of surface increase gradually in the models with fixed dip angles of the fault plane(model 1). However,when the horizontal projection distance exceeds 20 km,the influence of fault?s dip angle on the cumulative displacements of surface short-leveling will decrease significantly,and the cumulative displacements are maintained at about 1. 5 m. However,in the listric fault models(model 2),when the projection distance is less than 20 km,the listric fault structure impedes the sliding of fault. The short-leveling variation rate is only half of model 1;as a result,the ability to reflect the regional stress enhancement by cross-fault short-leveling is further weakened. But when the horizontal projection distance exceeds25 km,the cumulative displacements significantly increase,with the maximum displacement reaching 1. 75 m. The results of equivalent stress show that the listric fault structure causes a sudden increasement in equivalent stress when the horizontal projection distance is 10 km,higher equivalent stress values are accumulated between the projection distance of 5-20 km,and then high-low stress difference zones are formed at the bottom of the fault plane and near the transition zone of low-high dip angle.

Correlation of work function and stacking fault energy through Kelvin probe force microscopy and nanohardness in diluteα-magnesium

Electronic interactions of the Group 2A elements with magnesium have been studied through the dilute solid solutions in binary Mg-Ca,Mg-Sr and Mg-Ba systems.This investigation incorporated the difference in the‘Work Function'(ΔWF)measured via Kelvin Probe Force Microscopy(KPFM),as a property directly affected by interatomic bond types,i.e.the electronic structure,nanoindentation measurements,and Stacking Fault Energy values reported in the literature.It was shown that the nano-hardness of the solid-solutionα-Mg phase changed in the order of Mg-Ca>Mg-Sr>Mg-Ba.Thus,it was shown,by also considering the nano-hardness levels,that SFE of a solid-solution is closely correlated with its‘Work Function'level.Nano-hardness measurements on the eutectics andΔWF difference between eutectic phases enabled an assessment of the relative bond strength and the pertinent electronic structures of the eutectics in the three alloys.Correlation withΔWF and at least qualitative verification of those computed SFE values with some experimental measurement techniques were considered important as those computational methods are based on zero Kelvin degree,relatively simple atomic models and a number of assumptions.As asserted by this investigation,if the results of measurement techniques can be qualitatively correlated with those of the computational methods,it can be possible to evaluate the electronic structures in alloys,starting from binary systems,going to ternary and then multi-elemental systems.Our investigation has shown that such a qualitative correlation is possible.After all,the SFE values are not treated as absolute values but rather become essential in comparative investigations when assessing the influences of alloying elements at a fundamental level,that is,free electron density distributions.Our study indicated that the principles of‘electronic metallurgy'in developing multi-elemental alloy systems can be followed via practical experimental methods,i.e.ΔWF measurements using KPFM and nanoindentation.

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。

双馈异步发电机定子匝间短路对并联支路环流特性的影响

分析了双馈异步发电机定子匝间短路故障前后的定子绕组并联支路环流特性。首先对正常情况和匝间短路情况下气隙磁通密度表达式进行了推导,得到了并联支路环流的解析表达式;然后建立了故障前后的二维有限元计算模型并对并联支路环流进行求解计算;最后在故障模拟发电机组上完成了实验验证,所得实验结果与理论推导及有限元仿真结果基本吻合。结果表明:正常情况下发电机定子绕组无并联支路环流,而单条支路短路故障发生后并联支路内出现环流,其频率成分为f、f_()u、(1+(n±x)(1-s))f,并且随着故障程度的加剧各并联支路环流频率成分幅值将会增加;两条并联支路发生相同程度短路故障后无并联支路环流。

Saturnin-Short轻量级认证加密算法的统计无效故障分析

面向随机单字节故障模型和唯密文攻击假设,提出了一种针对Saturnin-Short算法的统计无效故障分析方法。该方法基于统计分布和无效状态分析,通过结合故障注入前后中间状态的变化,设计并采用了概率对称卡方-极大似然估计和调和中项-汉明重量新型区分器,最少仅需1097个无效故障并以不低于99%的成功率恢复Saturnin-Short算法的256 bit原始密钥。实验分析表明,所提区分器不仅降低了故障注入数,而且减少了攻击时间和复杂度。因此,Saturnin-Short算法不能抵抗统计无效故障分析的攻击。研究结果为其他轻量级认证加密算法的安全性分析提供了重要参考。

基于简短可验证环签名的区块链版权存证协议

在现有区块链版权存证系统中,各种环签名占用过多存储空间,数据共识算法效率有待提高。针对此问题,使用动态累加器对环成员公钥进行累加,分别设计初始化、系统选取、密钥生成、签名生成、签名验证等算法,构造多私钥生成器(PKG)的身份基简短可验证环签名方案;为主节点选取设置信用阈值,降低允许参与共识的最大节点数,改进已有的联盟链共识算法;利用所构环签名方案及改进的共识算法,提出一种新的区块链版权存证协议。对所构签名方案的不可伪造性及匿名性进行形式化证明;对所构签名方案的计算效率及存储空间进行分析和仿真,对存证系统的共识算法和容错性进行实验评估。结果显示:所提协议节省了签名时间开销和存储空间,提高了共识效率和容错性。

单向功率混合型MMC及其启动/直流短路故障穿越控制

单向功率传输场景下,挖掘桥臂内部全桥及半桥子模块的协调控制空间,提出可节省器件的类半桥子模块及由其与全桥子模块构成的新型单向功率混合型模块化多电平换流器(MMC)。针对启动阶段和直流短路故障穿越期间潜在的电容电压不均衡及电压、电流应力问题,提出适用于该拓扑的启动策略。基于直流环流注入控制实现直流短路故障穿越,保证设备在整个运行区域可靠运行。在MATLAB/Simulink中搭建仿真模型,验证所提控制策略的可行性和有效性。相比现有的混合型MMC,所提拓扑在保证直流短路故障穿越能力的前提下,节省半桥子模块内部的一个开关器件,具有较好的成本优势。

基于新型正序故障分量综合阻抗的有源配电网纵联保护

分布式电源接入配电网改变了传统配电网的拓扑结构,使故障特性发生了改变,常规的配电网电流保护将失去选择性。针对该问题,提出一种基于新型正序故障分量综合阻抗的有源配电网纵联保护方法。对不同类型分布式电源接入的线路发生区/内外故障时的正序故障电压、电流故障特征进行分析。利用区段两端电压、电流正序故障分量,构造两侧的线路推算阻抗,将它们相减后得到新型的综合阻抗。将综合阻抗与线路阻抗之比作为阻抗系数,进而构造区、内外短路故障的保护判据。通过大量仿真验证了所提保护算法的有效性,其能够准确地检测出短路故障,不受故障类型、故障位置、分布式电源类型、渗透率、分布式电源退出的影响,具有较强的抗过渡电阻能力,且灵敏度较高。

基于EEMD与CNN-BiLSTM的噪声环境下滚动轴承故障诊断方法

针对滚动轴承在噪声环境中发生故障时,传统深度神经网络容易出现特征提取不充分,过拟合,泛化能力不足的问题,提出一种集成经验模态分解(EEMD)与卷积神经网络-双向长短时记忆网络(CNN-BiLSTM)的故障诊断方法。在信号预处理阶段使用EEMD将噪声环境下的振动信号分解为一系列固有模态函数,降低噪声的影响;在CNN部分的第1层使用大卷积核与多分支结构获得不同的感受野,在每一个分支中随机丢弃一些数据增强模型的抗干扰能力,从而提取到更具泛化能力的多样化特征信息,后续部分使用残差结构,以免网络较深时发生梯度消失的现象,解决深层次网络退化问题;在BiLSTM部分使用2个并行的分支结构,用于增强模型对时序信息的利用,从而提高模型在不同工况和噪声环境下的准确率。使用凯斯西储大学轴承数据集和西安交通大学轴承数据集对所提方法进行验证,并与其他深度学习方法和传统机器学习方法进行对比,结果表明本文方法在多种工况和噪声环境下均取得了优异的故障诊断性能。

基于三有源桥串并联潮流控制器的双极直流配电网主动限流策略

直流潮流控制器是解决环网式直流配电网的线路潮流不完全可控的有效技术手段。然而,现有方法未能充分发掘其在故障限流中的潜力。该文建立了三有源桥串并联潮流控制器(triple active bridge power flow controller,TAB-PFC)的故障模量分析模型,提出一种基于TAB-PFC的双极直流配电网主动限流策略。首先阐述了TAB-PFC的限流原理,提出基于TAB-PFC的主动限流控制策略。然后对TAB-PFC不同故障阶段进行建模,并计及极间互感构建含TAB-PFC的双极直流配电网故障模量等效模型。在此基础上,分析不同参数对TAB-PFC的限流能力的影响,为其参数选取提供依据。在MATLAB/Simulink搭建了含TAB-PFC的双极直流配电网模型,验证了所提主动限流策略的有效性及故障等效电路模型和参数分析的正确性。

一种航空发电机电枢绕组匝间短路故障诊断技术

【目的】针对航空发电机电枢绕组匝间短路故障诊断问题,本文提出一种基于卷积神经网络(CNN)和压缩-激励(SE)注意力机制以及双向长短期记忆(BiLSTM)网络的诊断方法,以提高电枢绕组故障诊断的有效性和鲁棒性。【方法】首先,建立了电励磁双凸极发电机(DSEG)电枢绕组匝间短路的等效解析模型,采用发电机机壳表面振动信号作为故障特征信号,对影响振动特性的气隙磁密和电磁力波的表达式进行了理论推导。然后,通过Workbench有限元软件仿真分析了各种短路条件下电磁力波对振动特性的影响。最后,对振动信号进行采集,将其作为实际试验数据并提取相关故障特征,通过将这些提取的特征输入CNN-SE-BiLSTM,系统有效地实现了故障诊断。其中,CNN和BiLSTM网络可以有效提取振动信号中的局部特征和时序特征;SE注意力机制可以进一步优化特征权重分配,通过选择性放大相关诊断特征,显著增强了模型的故障诊断能力。【结果】试验结果表明,所提基于CNN-SE-BiLSTM的故障诊断方法在多种工况下对电枢绕组匝间短路故障的诊断准确率均超过99%,且在噪声环境中仍能表现出良好的诊断性能。与传统诊断方法相比,所提方法在各种转速和负载条件下具有更强的抗干扰能力、更高的故障识别精度以及更快的诊断速度,进一步验证了该方法在航空航天发电机复杂工况下的适用性。【结论】本文所提CNN-SE-BiLSTM诊断方法有效提高了DSEG系统的故障诊断效率和准确性。通过将用于空间特征提取的CNN、用于选择性特征加权的SE注意力机制以及用于捕捉综合时间信息的BiLSTM相结合,该方法为诊断匝间短路故障提供了一种精简而高效的解决方案。

双极短路故障下基于暂态能量抑制的MMC-HVDC电网限流设备的参数优化

模块化多电平换流器高压直流输电电网发生直流短路故障时,具有故障电流上升速率快、峰值高等特征,会严重危害电网安全。为了抑制故障电流发展,缓和高压直流断路器开断电流大小与故障切除时间之间的矛盾,需要在直流侧配置限流设备。首先,研究双极短路故障下不同类型限流设备的工作机理,并从暂态能量的角度探讨能量释放源的分布情况、暂态能量的演化特征及限流设备参数对其限流能力的影响;其次,提出基于NSGA-Ⅱ优化算法的故障限流器与直流电抗器参数优化配置计算方法;最后,在PSCAD/EMTDC仿真系统中搭建四端双极柔性直流电网模型,针对不同电气需求的应用场景,设计相应的限流设备参数优化方案。仿真测试结果表明,该优化方法能够正确地配置限流设备的参数,提高限流设备对暂态能量的抑制效率,验证了所提方法的有效性与可靠性。

基于卷积双向长短期记忆网络的微网继电保护故障诊断技术

分布式电源种类和容量不断提升的微网运行方式复杂、故障特征微弱,现有的继电保护装置故障诊断方法无法满足保护需求。提出一种基于卷积双向长短期记忆网络的微网继电保护故障诊断技术。首先,分析多能源互补微网系统架构,对采集的三相电流数据进行预处理,提高后续模型对数据的学习效率;然后,融合卷积神经网络和双向长短期记忆网络提出卷积双向长短期记忆网络的微网继电保护故障诊断方法,提取三相电流数据长序列和局部序列特征实现故障分类、故障定位,融合注意力机制,重点关注对故障诊断有影响的特征,提高故障诊断准确率;最后经过RTDS实时仿真系统进行验证,实验结果表明,所提方法故障诊断精度高、计算时间短,同卷积神经网络、长短期记忆网络、人工神经网络相比,故障分类准确率分别提升8.53%、9.62%、11.45%,故障定位准确率分别提升7.47%、10.61%、10.85%,验证所提方法的有效性与先进性。

基于数字孪生的风电机组齿轮箱故障诊断方法研究

风力发电作为可再生能源的重要支柱,其风电机组齿轮箱受多种因素影响易出现故障,从而影响整个风电机组的稳定性。因此,提出基于数字孪生的风电机组齿轮箱故障诊断方法。首先,构建数字孪生总体架构。其次,采集风电机组齿轮箱数据并过滤,利用集合经验模态分解提取特征。最后,构建风电机组的齿轮箱的数字孪生模型,并采用长短期记忆(Long Short-Term Memory,LSTM)完成故障诊断。实验结果表明,所提方法故障诊断的准确率在0.94以上、漏报率在0.15以下,为风电场的运维管理提供了有力的决策支持。

农机电气系统短路与断路故障分析及维修方法

农机电气系统掌控着机械设备的启动、运行监测、功能执行等诸多核心环节,其稳定、可靠运行对于保障农机整机性能与作业连续性举足轻重。在分析农机电气系统短路与断路故障原因的基础上,论述了短路与断路故障的维修方法,并对电气系统短路与断路故障维修的效果进行了分析。

机器学习下配电网短路故障快速智能恢复方法研究

由于配电网短路故障产生的运维成本逐年增加,影响电力企业整体经济效益,为此提出机器学习下配电网短路故障快速智能恢复方法。分析回声状态网络,建立配电网短路故障恢复模型;设置配电网运行指标约束条件,构建回声状态网络目标函数,计算函数中个体与约束条件间的违背程度,得到实际目标函数;在目标优化阶段,保证重要负荷最大化,再考虑配电网运行均衡度,以此实现配电网短路故障快速智能恢复。对所提方法展开实验测试,结果表明,所提方法可有效恢复故障支路和节点,同时恢复后电压、电流波动均保证在所允许的范围内。