Single Phase-to-Ground Fault Line Identification and Section Location Method for Non-Effectively Grounded Distribution Systems Based on Signal Injection

A diagnostic signal current trace detecting based single phase-to-ground fault line identifica- tion and section location method for non-effectively grounded distribution systems is presented in this paper.A special diagnostic signal current is injected into the fault distribution system,and then it is detected at the outlet terminals to identify the fault line and at the sectionalizing or branching point along the fault line to locate the fault section.The method has been put into application in actual distribution network and field experience shows that it can identify the fault line and locate the fault section correctly and effectively.

Single event effects evaluation on convolution neural network in Xilinx 28 nm system on chip

Convolutional neural networks(CNNs) exhibit excellent performance in the areas of image recognition and object detection, which can enhance the intelligence level of spacecraft. However, in aerospace, energetic particles, such as heavy ions, protons, and alpha particles, can induce single event effects(SEEs) that lead CNNs to malfunction and can significantly impact the reliability of a CNN system. In this paper, the MNIST CNN system was constructed based on a 28 nm systemon-chip(SoC), and then an alpha particle irradiation experiment and fault injection were applied to evaluate the SEE of the CNN system. Various types of soft errors in the CNN system have been detected, and the SEE cross sections have been calculated. Furthermore, the mechanisms behind some soft errors have been explained. This research will provide technical support for the design of radiation-resistant artificial intelligence chips.

Fault tolerant control of electric pitch control system based on single current detection

In view of the current sensors failure in electric pitch system,a variable universe fuzzy fault tolerant control method of electric pitch control system based on single current detection is proposed.When there is single or two-current sensor fault occurs,based on the proposed method the missing current information can be reconstructed by using direct current（DC）bus current sensor and the three-phase current can be updated in time within any two adjacent sampling periods,so as to ensure stability of the closed-loop system.And then the switchover and fault tolerant control of fault current sensor would be accomplished by fault diagnosis method based on adaptive threshold judgment.For the reconstructed signal error caused by the modulation method and the main control target of electric pitch system,a variable universe fuzzy control method is used in the speed loop,which can improve the anti-disturbance ability to load variation,and the robustness of fault tolerance system.The results show that the fault tolerant control method makes the variable pitch control system still has ideal control characteristics in case of sensor failure although part of the system performance is lost,thus the correctness of the proposed method is verified.

Comparison between open phase fault of arc suppression coil and single phase to earth fault in coal mine distribution network

When, in a coal mine distribution network whose neutral point is grounded by an arc suppression coil (ASC), a fault occurs in the ASC, compensation cannot be properly realized. Furthermore, it can damage the safe and reliable run of the network. We first introduce a three-phase five-column arc suppression coil (TPFCASC) and discuss its autotracking compensation theory. Then we compare the single phase to ground fault of the coal mine distribution network with an open phase fault at the TPFCASC using the Thévenin theory, the symmetrical-component method and the complex sequence network respectively. The results show that, in both types of faults, zero-sequence voltage of the network will appear and the maximum magnitude of this zero-sequence voltage is different in both faults. Based on this situation, a protection for the open phase fault at the TPFCASC should be estab-lished.

Novel Fault Detection Optimization Algorithm for Single Event Effect system Based on Multi-information Entropy Fusion

Fault detection caused by single event effect( SEE) in system was studied,and an improved fault detection algorithm by fusing multi-information entropy for detecting soft error was proposed based on multi-objective detection approach and classification management method. In the improved fault detection algorithm, the analysis model of posteriori information with corresponding multi-fault alternative detection points was formulated through correlation information matrix, and the maximum incremental information entropy was chosen as the classification principle for the optimal detection points. A system design example was given to prove the rationality and feasibility of this algorithm.This fault detection algorithm can achieve the purpose of fault detection and resource configuration with high efficiency.

Detection and Diagnosis of Gear Fault By the Single Gear Tooth Analysis Technique

This paper presents a procedure of sing le gear tooth analysis for early detection and diagnosis of gear faults. The objec tive of this procedure is to develop a method for more sensitive detection of th e incipient faults and locating the faults in the gear. The main idea of the sin gle gear tooth analysis is that the vibration signals collected with a high samp ling rate are divided into a number of segments with the same time interval. The number of signal segments is equal to that of the gear teeth. The analysis of i ndividual segments reveals more sensitively the changes of the vibration signals in both time and frequency domain caused by gear faults. In addition, the locat ion of a failed tooth can be indicated in terms of the position of the segment t hat deviates from the normal segments. An experimental investigation verified th e advantages of the single gear tooth analysis.

Multiscale Simulation of the Dislocation Emissions of Single Ni Crystal in Nanoindentation

The simulation of nanoindentation into single nickel crystal is performed by using quasi continuum method.The strain energy-displacement and load-displacement curves are presented to study the mechanical behavior of the dislocation nucleation.The characteristics of the stacking fault and dislocation nucleation are determined by calculating the centro-symmetry parameters and analyzing the displacement field of the atoms beneath the indenter.The structure of the stacking fault and the characteristics of dislocation obtained in the simulation by quasicontinuum method are reproduced in the simulation by molecular dynamics.

基于Single-Term函数的FPGA互连资源故障高速诊断

针对面向应用的FPGA互连资源的BRIDGING桥接故障诊断,文中提出的利用SingleTerm函数故障检测结果测试方法。对于使用LUT的电路,本方法可以诊断单个互连资源STUCK-AT故障或者BRIDGING桥接故障,并可以把诊断BRIDGING桥接故障的测试配置次数减少50%左右。通过对于应用基准电路的仿真实验,验证本方法有效。

基于FTU的配电网单相接地故障定位与恢复方法

配电网发生最多的故障是接地故障。针对准确地检测隔离接地故障线路并尽快恢复供电,提出基于配电开关监控终端(FTU)的配电网单相接地故障定位与恢复方法。利用配电网各节点FTU的小波包变换暂态选线及相电流暂态特征选线技术,结合故障路径自适应处理控制策略,配合首开关延时合闸逻辑,从而实现多分支配电网故障定位与自动隔离恢复。所提方法能够快速选出故障线路并隔离故障区段,有利于故障快速消除,提高系统运行的安全性、可靠性。

高含水复杂断块油藏单层系边外注水开发模式

复杂断块油藏在开发后期面临综合含水率高、地层能量不足、剩余油分布复杂、井网适应性差等问题。以济阳坳陷沾化凹陷中部垦71断块油藏为例,基于水驱油藏的油包水和水包油2种油水分布状态,利用理论模型推导和数值模拟方法,开展了单层系边外注水开发模式研究。结果表明:从采液端和注水端的受力分析可获得单层系开发的合理注水量、合理采液量和合理注采井距,单层系开发的合理注水压差、合理注水量、合理采液量是影响其剩余油饱和度、含水饱和度的关键因素,对油层合理地层压力水平及剩余油二次富集起主要控制作用。通过加大注采井距至油水边界外围,以2.9倍含油条带宽度为合理注采井距的临界值,采用短注长静置的非对称周期注采方式,建立单层系边外注水开发模式,有利于保持单层系的压力系统稳定和提高剩余油波及率,从而提高原油采收率。矿场实践表明,采用单层系边外注水开发模式后,垦71断块油藏日产油量提高至254 t/d,含水率控制在93.7%,采收率提高至31.53%,采油速率提高4.9%,显示出良好的增产效果。单层系边外注水开发模式解决了高含水复杂断块油藏开发中的剩余油分布分散、水驱波及率低和井网适应性差等难题,可为复杂断块油藏开发提供指导和借鉴。

基于行波全景特征深度挖掘的单端故障定位方法

现有的故障定位方法基于局部波头故障特征,存在微弱故障(过零点附近故障、高阻接地故障)和母线出口处故障定位失败的技术瓶颈。为此,论文提出一种基于行波全景特征深度挖掘的单端故障定位方法。首先,基于时频域行波全景波形,理论和仿真论证了时域各次波头到达时序能反映不同故障区段,各次波头频率分布能反映故障位置,定性分析了行波全景波形与故障位置一一对应的映射机理,论证了行波全景波形唯一性理论;然后,以时频域故障全景波形为输入特征量,利用轻量级LeNet-5模型构建卷积神经网络(convolution neural network,CNN),并采用3×3小尺寸卷积核挖掘全景波形故障特征,建立全景波形特征量与故障距离的映射关系,实现精确故障定位;最后,利用激活热力图可视化技术展现CNN各卷积通道挖掘全景波形故障敏感特征,有力论证了所提方法具有强适应性的内在原因。仿真结果表明该文所提方法具有较高的定位精度,特别是针对微弱故障和母线出口处故障具有较强的算法适应性,故障定位平均绝对误差为99.855 m。

基于有源消弧暂态衰减信息的配电网接地故障跟踪检测方法

现有配电网单相接地故障检测技术缺乏消弧过程的故障程度跟踪与选线能力。该文充分利用消弧过程中的暂态信息,建立考虑线路参数不对称的集总参数等效模型,论证消弧过程零序电压衰减直流特征的物理意义,提出考虑快速消弧的配电网故障检测新方法,对于低、高阻接地故障均有较高的检测灵敏度。实际应用中,仅需观测消弧全补偿电流投切过程中零序电压及零序电流波形,即可实现过渡电阻测量、故障程度跟踪与故障选线,具有瞬时性故障实时跟踪、故障检测与故障消弧同步进行的优势,操作简单、易于实现。仿真实验证实了方法的有效性,为配电网故障检测提供了新的理论依据。

基于限流电抗器两侧特定频段暂态能量比的MTDC电网单端量保护方案

柔性直流输电技术有利于未来大量分布式能源接入电网,而配置快速、可靠的保护方案是柔性直流技术发展的关键。基于直流电网等效模型,提出一种基于限流电抗器两侧电压特定频段暂态能量比差异性的单端量故障区域识别方法。该方法依据贝瑞隆等效模型计算出限流电抗器两侧电压比,通过广义S变换提取限流电抗器两侧特定频段电压,根据故障时正负极限流电抗器的电压幅值差的差异性实现故障选极。最后在PSCAD/EMTDC平台搭建仿真模型,分析出发生区内外故障时差异性明显,具备较强的耐过渡电阻与抗噪声干扰能力。

风电场集电线路单相接地故障柔性电压消弧与动态保护新原理

为解决风电场集电系统长期存在的线路单相接地故障处理难题,提出风电场中性点柔性接地方式,理论推导获得柔性接地风电场三序等效电路,与集电线路单相接地故障复合序网模型,建立风电场零序电压柔性调控理论,提出集电线路单相接地故障柔性电压消弧方法,可主动将故障点电压及故障残流迅速抑制到零,实现单相接地故障电弧的可靠消除。进一步提出基于零序电流动态增量的高阻故障辨识与保护方法,通过柔性调控零序补偿电流,逐渐放大故障残流,实现永久性单相接地故障的灵敏感知与保护。利用PSCAD/EMTDC搭建含双馈异步风电机(doubly-fedinduction generator,DFIG)的规模化风电场模型,模拟多种运行与故障条件对所提方法进行验证,仿真结果表明,该方法能够在考虑系统不平衡电压的情况下精准调控集电线路故障点电压,实现瞬时性单相接地故障快速可靠消弧,动态感知并持续抑制永久性单相接地故障残流,实现集电线路高阻接地故障的灵敏保护。该技术有望提升风电场运行灵活性与故障防御能力,有力保障新能源电能外送的持续性、可靠性。

单相脉冲整流器故障在线智能诊断实验设计

针对高速列车电力牵引系统中单相脉冲整流器的功率器件开路故障和传感器故障,设计了基于数据驱动的故障在线智能诊断实验。首先,对单相脉冲整流器系统进行数学建模,分析功率器件开路故障的故障拓扑和传感器故障的故障机理;然后,基于极限学习机算法和非线性自回归结构设计智能诊断模型,并将故障在线智能诊断实验分为离线训练和在线验证2个阶段;最后,基于RT Box半实物仿真器搭建快速原型控制实验平台,对故障模型和诊断模型进行实验验证。实验结果表明,构建的单相脉冲整流器故障在线智能诊断模型可以在1/4个基波周期内检测到故障的发生,并在3/4个基波周期内识别出具体故障类型。

基于限流电抗器电压的直流配电网单端量保护

直流配电网故障特性复杂,故障电流上升速度快且峰值大,快速、灵敏的故障识别与线路保护是保障直流配电网安全运行的关键技术之一。为此,针对增设限流电抗器的直流配电网,提出一种利用限流电抗器电压实现高灵敏故障识别的直流配电网单端量保护方案。首先,通过分析含限流电抗器的直流配电网故障特性,明确区内、区外故障时限流电抗器电压的特征差异。其次,研究限流电抗器对故障特性及直流保护的影响机制,提出虚拟补偿策略以增强故障识别的灵敏性。在此基础上,根据线路电压变化率设计保护启动判据,提出基于虚拟补偿的故障识别判据和故障选极判据,并给出完整的保护方案流程。最后,基于PSCAD/EMTDC仿真平台进行大量的仿真测试,结果表明所提保护方案能够实现对直流故障的快速准确判断,无需通信支持,且对过渡电阻、噪声及负荷波动具有较强的耐受能力。

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。

不同稳态工况对同步调相机单相短路后暂态温升的影响

同步调相机可在系统故障时为特高压直流换流站提供暂态无功支持,以保持系统电压稳定,防止直流换相失败,但调相机的高无功输出也会导致其温升增加,运行能力受限。系统故障前同步调相机的初始工况是影响其暂态温升和运行能力的一个重要因素,为研究系统低电压时调相机暂态温升与初始工况之间的关系,该文将调相机的电磁场、温度场与电网模型耦合,计算调相机不同稳态工况下的定转子损耗和温度分布;以线路单相短路故障引起的系统低电压为例,研究调相机初始工况对暂态温升的影响。在考虑各结构件最大容许温度的条件下,揭示调相机单相短路持续时间随初始工况的变化规律。研究结果为提升调相机在系统低电压下的暂态运行能力提供技术支持。

单一模态稀疏字典的压缩感知故障诊断方法

针对压缩感知的算法流程中,传统的稀疏表示字典存在体量庞大、占用内存严重、构造效率低等问题,提出了一种基于单一模态Laplace小波字典的压缩感知故障诊断方法。首先,截取长信号中的特征片段,采用滑动频谱有效值识别信号的共振频带及中心频率,确定Laplace小波的模态频率;其次,根据滑动峭度指标的分布曲线,提取包含单一冲击的片段信号,通过相关滤波法提取Laplace小波的模态阻尼;然后,通过补零插值建立特定长度的冲击原子,并基于循环移位策略,扩张成单一模态的Laplace小波稀疏字典;最后,结合高斯随机测量矩阵和正交匹配追踪算法,实现原始信号的压缩重构。仿真和实验结果表明,单一模态的小波字典具有更高的构造效率,占用内存更低,能够实现数据的有效压缩和特征重构,确保了噪声环境下的故障特征辨识。