Research on Magnetically Coupled Resonant Detection Method for Breakpoint of Four Mesh Grounding Grid

Magnetically coupled resonant technology is a novel method for solving the breakpoint locating of power grounding grid.But the method can only detect breakpoints of a single mesh grounding grid at present.In this paper,a magnetically coupled resonant detection method for four-hole grounding grid breakpoint is proposed.Firstly,the equivalent circuit model of the four mesh grounding grid with two types of breakpoints,namely edge branch and intermediate branch,is established.The input impedance and phase angle of the system are obtained by analyzing the equivalent capacitance and equivalent resistance in the model.Secondly,the magnetically coupled resonant physical process of grounding grid faults is solved via HFSS software.The magnetic field intensity and phase frequency characteristic curves of four mesh holes with different branches and positions of breakpoints and different corrosion degrees are studied,and an experimental system is built to verify the feasibility.The results show that under the condition of grounding grid buried depth of 0.5 m and input frequency of 1~15MHz,and there is an inverse relationship between equivalent capacitance and distortion frequency,the phase angle is positively correlated with the degree of corrosion of grounding grid,and the error of signal distortion frequency can be positioned at 5%.This paper provides some ideas for the application of magnetic coupling grounding grid detection technology.

Adaptive Control of Helicopter Ground Resonance with Magnetorheological Damper

The methodology for adaptive control of helicopter ground resonance with magnetorheological （MR） damper is presented. The adaptive inverse control method is used to control the output damping force of MR damper and the range of the damping force is given. Through the adaptive inverse control, the damping force of MR damper is fit to a desired damping force. With the background of applying MR damper to control of helicopter ground resonance, a model of loss force and an adaptive arithmetic for stabilization of the coupled rotor/fuselage system are presented. The simulation shows that the controller presented in this paper can stabilize the rotor/fuselage coupling system quickly and control the helicopter ground resonance effectively.

Small-current grounding fault location method based on transient main resonance frequency analysis

The small-current grounding fault in distribution network is hard to be located because of its weak fault features.To accurately locate the faults,the transient process is analyzed in this paper.Through the study we take that the main resonant frequency and its corresponding component is related to the fault distance.Based on this,a fault location method based on double-end wavelet energy ratio at the scale corresponding to the main resonant frequency is proposed.And back propagation neural network(BPNN)is selected to fit the non-linear relationship between the wavelet energy ratio and fault distance.The performance of this proposed method has been verified in different scenarios of a simulation model in PSCAD/EMTDC.

OPTIMIZATION DESIGN FOR SUPPRESSING "GROUND RESONANCE" OF THE HELICOPTER

The design problem for suppressing 'ground resonance' of the helicopter, with which few researchers have concerned so far, is studied in this paper. Based on the ideas of pole region placement in control theory and of optimization, the method for optimally designing the stiffness and damping parameters of the system with satisfying specified requirements is presented. The effective design criteria and procedures are presented according to the principle of 'ground resonance'.For illustrating the method presented in this paper three typical calculation modes are studied. The results are satisfactory.

A STUDY ON MECHANICAL MODEL OF THE HELICOPTER "GROUND RESONANCE

The key problem to the calculation and optimization design of the helicopter 'Ground Resonance' is to correctly build up a mechanical model. In the past, the literature was only concerned with the lag modes of the rotor blade and the flap modes were neglected. But such approaches should be reconsidered now. In order to study the influences of rotating multiblades rotor on the degrees of freedom and also the flap ''Ground Resonance' of a helicopter, it is necessary to consider not only the lag degrees of freedom but also the flap degrees of freedom. Using Lagrangian equation a dynamical equation of the space model for helicopter 'Ground Resonance'is deduced for the first time. Some computation results show that the mechanical model including both lag DOF and flap DOF is more reasonable.

Comparing High-resistance Grounding Method with Resonance Grounding Method for Large Generators

For large generators, the problem of high-resistance grounding method and the advantages of resonance, grounding method are discussed in detail, and an overall comparison is given in this paper. It is recommended that the latter should be adopted so as to increase the operation reliability of large generators and power systems.

基于零序特征参量差异的谐振接地系统熄弧时刻判别方法

在谐振接地系统中,熄弧时刻的准确判别对于接地故障的选线、消弧效果评估以及熄弧后暂态信息提取和利用具有指导意义。该文针对谐振接地系统单相接地故障,分析了故障点工频电流熄弧前后的故障电气特征,并利用母线零序电压和消弧线圈电流,通过求取其信号的一阶导数及其平方信号的二阶导数,构造两种特征参量。研究发现该特征参量在熄弧前为常数,熄弧后发生明显变化,据此可形成相应的熄弧时刻判别的基本判据。考虑到系统实际运行中各种因素的影响,在此基础上形成熄弧时刻判别的附加判据,从而最终提出基于零序特征参量差异的谐振接地系统熄弧时刻判别方法。通过Mat Lab/Simulink仿真和现场实测,验证了该熄弧时刻判别方法的有效性和准确性。

并阻尼谐振接地系统对地参数测量与高阻故障选线新方法

针对谐振接地系统对地参数测量不准确以及高阻接地故障选线困难的问题,提出了并阻尼谐振接地系统对地参数测量与高阻故障选线新方法。基于消弧线圈并联阻尼电阻的投切特性,利用投切阻尼电阻前后零序电压幅值与相位的变化关系,测量系统对地电导与电容参数。在系统正常运行时,通过调整并联阻尼电阻值大小,测量各馈线零序导纳值。在发生接地故障后退出阻尼电阻,测量故障后各馈线零序导纳值,可消除系统参数不对称、互感器采样不同步的影响,主动构造故障前后各馈线的零序导纳相角差,实现故障线路的准确判别。在PSCAD仿真环境下对所提方法进行验证,结果表明:所提方法能够精确测量对地电导与电容参数,测量相对误差不高于0.6%;在不同馈线、不同过渡电阻下发生接地故障时,能准确判别故障线路,耐过渡电阻能力达10 kΩ。

基于多维波形差异度聚类分析的配电网故障区段定位方法

谐振接地系统运行环境繁杂,单相接地故障发生状态多变,基于单一特征量的传统配电网故障区段定位方法存在各自的定位判别盲区,方法可靠性和适用性难以保障。针对上述问题提出了一种无需整定的基于多维波形差异度聚类分析的配电网故障区段定位方法。依据故障点上下游各检测点零序电流暂态及稳态分量的波形差异性特征,通过离散Fréchet距离算法量化相邻检测点间的暂态及稳态波形差异度,并采用模糊C均值算法(fuzzyC-means,FCM)综合多特征信息以区分正常区段与故障区段,有效消除了单一特征定位盲区,实现故障区段自适应准确定位。PSCAD/EMTDC仿真结果以及10kV真型实验结果表明所提方法不仅保证了在不同故障工况下的定位可靠性和适用性,还具有耐高阻能力强、抗噪性高等优点。

探地雷达介质谐振天线的原理研究

为了增加探地雷达的探测深度,提高探地雷达增益,本文从物理学中周期性力作用下的阻尼振动的角度出发,推导周期信号作用下电磁波在介质谐振天线中的谐振过程,阐述了天线的基本工作原理,并对其谐振放大作用进行了仿真.研究发现,在周期信号作用下,天线谐振腔内的信号通过谐振形成驻波实现能量增强,证明了以时间换取能量是可行的.这种谐振放大作用使天线具有更高的辐射功率,对解决探地雷达的探深问题具有重要意义.

基于多频带多特征融合的配电网单相接地故障选段方法

针对现有配电网单相接地故障选段方法存在的通信负担重、阈值设置困难及故障特征量单一等问题,提出一种基于多频带多特征融合的配电网单相接地故障选段方法。首先,利用小波包变换分别对故障后首半个工频周期的零序电压导数和零序电流进行分解和重构,得到原始波形的不同频带分量。其次,根据不同频带分量间的极性关系分别引入伏安特性特征向量与零序功率累加和作为故障特征。最后,筛选特征频带并构造基于特征频带与故障特征融合的选段判据。仿真实验及现场数据验证结果表明,所提方法能够有效实现单相接地故障免阈值就地选段。

Faulty Feeder Identification in Resonant Grounding Distribution Networks Based on Deep Learning and Transfer Learning

Identification of faulty feeders in resonant grounding distribution networks remains a significant challenge dueto the weak fault current and complicated working conditions.In this paper, we present a deep learning-based multi-labelclassification framework to reliably distinguish the faulty feeder.Three different neural networks (NNs) including the multilayerperceptron, one-dimensional convolutional neural network (1DCNN), and 2D CNN are built. However, the labeled data maybe difficult to obtain in the actual environment. We use thesimplified simulation model based on a full-scale test field (FSTF)to obtain sufficient labeled source data. Being different frommost learning-based methods, assuming that the distribution ofsource domain and target domain is identical, we propose asamples-based transfer learning method to improve the domainadaptation by using samples in the source domain with properweights. The TrAdaBoost algorithm is adopted to update theweights of each sample. The recorded data obtained in the FSTFare utilized to test the domain adaptability. According to ourvalidation and testing, the validation accuracies are high whenthere is sufficient labeled data for training the proposed NNs.The proposed 2D CNN has the best domain adaptability. TheTrAdaBoost algorithm can help the NNs to train an efficientclassifier that has better domain adaptation. It has been thereforeconcluded that the proposed method, especially the 2D CNN, issuitable for actual distribution networks.

铁路地面信号产品振动试验标准分析与应用

本文分析了铁路地面信号产品振动试验标准的关键技术参数,阐述了试验等级和参数选择;在标准应用方面,详细介绍了振动设备选择、振动试验实施流程以及典型试验参数设置等内容。通过本文的研究,有助于快速了解标准的要点、难点,有助于检测人员详细了解试验,从而提高试验过程的一致性、试验结果的准确性和可靠性。

滑橇式直升机地面共振非线性时域仿真

为研究非线性因素对滑橇式直升机地面共振的影响,针对滑橇式起落架弹性结构及机体阻尼器连接方式的特点,建立了简洁有效的直升机地面共振当量平面模型。该模型不仅计入了桨叶减摆器以及机体阻尼器的非线性,还考虑了机体阻尼器非比例阻尼对机体固有特性的影响。通过激振法激出机体模态稳态响应,并采用模态阻尼识别法对瞬态响应进行模态阻尼识别。分析可知,机体阻尼器提供的非比例非线性阻尼使得机体模态阻尼在时域上呈现较复杂的变化,系统稳定时,激出的阻尼器稳态响应速度幅值越大,其变化就越滞后。

Application of geophysical methods in fine detection of urban concealed karst:A case study of Wuhan City,China

The construction of modern livable cities faces challenges in karst areas,including ground collapse and engineering problems.Wuhan,with a population of 13.74×10^(6) and approximately 1161 km^(2)of soluble rocks in the urban area of 8569.15 km^(2),predominantly consists of concealed karst areas where occasional ground collapse events occur,posing significant threats to underground engineering projects.To address these challenges,a comprehensive geological survey was conducted in Wuhan,focusing on major karstrelated issues.Geophysical methods offer advantages over drilling in detecting concealed karst areas due to their efficiency,non-destructiveness,and flexibility.This paper reviewed the karst geological characteristics in Wuhan and the geophysical exploration methods for karst,selected eight effective geophysical methods for field experimentation,evaluated their suitability,and proposed method combinations for different karst scenarios.The results show that different geophysical methods have varying applicability for karst detection in Wuhan,and combining multiple methods enhances detection effectiveness.The specific recommendations for method combinations provided in this study serve as a valuable reference for karst detection in Wuhan.

基于缺陷地和开口谐振环的三频段小型化天线

提出了一种新型三频段工作的小型微带贴片天线,天线采用不对称结构,在接地板上引入缺陷地结构(DGS)改变了天线表面电流分布,改善工作频率,衍生在无线局域网(WLAN)(2.4 GHz)处的频带。加载开口谐振环(SRR)金属环结构在独立控制WLAN(5.8 GHz)的频带的同时,减小了12%的天线体积。天线结构紧凑,整体尺寸为12.5 mm×28.5 mm×1.5 mm。结果表明,天线覆盖3个独立的阻抗带宽,分别为800 MHz(1.96~2.76 GHz),200 MHz(5.65~5.85 GHz)和1 460 MHz(7.64~9.1 GHz),在频段内的回波损耗均小于-10 dB,具有良好的方向性和增益,支持WLAN(5.8/2.4 GHz)频段和国际电信联盟(ITU)(8.0~8.7 GHz)频段的应用。

基于机体当量化的滑橇式直升机地面共振分析

针对滑橇式直升机不便于建立空间模型进行地面共振分析的问题,提出了基于有限元将机体参数当量至桨毂中心,当量结果可通过扫频激振试验验证,再采用平面模型进行地面共振分析的方法。采用所计算的当量参数对某型滑橇式直升机地面共振进行仿真分析,结果表明:该型机机体一阶模态与旋翼摆振后退型模态的共振转速在旋翼启动加速过程中可能达到,但系统具有足够的阻尼确保不发生地面共振;机体二阶以上模态与旋翼摆振后退型模态的共振转速远大于额定转速,不会引发地面共振。

基于K均值聚类算法的谐振接地系统故障区段定位方法

现有的谐振接地配电网单相接地故障定位方法存在通信依赖过度、特征分析复杂和阈值设置困难等问题,现场运行的适用性较低。本文基于深度融合智能开关在配电网中的应用,研究三相电流变化量的波形特征,提出基于K均值聚类算法的就地选段方法。该方法提取各区段数据特征量,发挥K均值聚类算法无监督学习的优点,使各检测节点只需处理本地故障信号,从而减轻通信压力。利用仿真和现场数据验证该方法的可行性,结果表明,该方法在多种故障工况下都表现出较高的可靠性,并且能够较好地适应现场环境。

一起化工厂10kV开关柜过电压保护器热崩溃事故分析

以某化工厂110kV变电站10kV开关柜内过电压保护器热崩溃引发断路器跳闸、开关柜电缆室爆炸的事故为例,从过电压保护器结构及工作原理入手,根据事故现象对事故发生原因进行逐一排查和分析,综合判断造成这起事故的原因为10kV系统B相反复间歇电弧接地引发铁磁谐振过电压,导致过电压保护器内氧化锌电阻片热崩溃,继而引发开关柜内AC相间短路故障和电缆室爆炸,分析结果表明该型过电压保护器的三相四星形接线结构缺陷是此次事故发生的根源。最后,为防止类似事故再次发生,提出消除和防范措施,为确保电力系统安全稳定运行提供参考。

基于零序导纳幅值比的同母两回线异相接地复故障选线方法

消弧线圈接地系统发生同母两回线异相接地故障时,常规选线装置存在准确率不高的问题。针对消弧线圈接地系统发生的同母两回线异相接地复故障选线难的问题,文中通过线路首端的零序电流和母线零序电压信息获得线路的零序导纳,分析消弧线圈接地系统发生同母两回线异相接地故障特征,发现故障线路零序导纳的幅值大于非故障线路零序导纳的幅值,在高阻接地时仍呈现出此特征。在此基础上提出了基于零序导纳幅值比的消弧线圈接地系统同母两回线异相接地复故障选线方法,利用故障线路与非故障线路零序导纳幅值的差异建立故障选线判据,将所有故障线路全部选出。PSCAD仿真结果表明,该选线方法准确率高,不受故障位置、消弧线圈补偿度的影响,具有较强的耐受过渡电阻的能力。