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文章详细介绍了针对当前医院使用的由为数众多的计算机构成的各种网络,以及运用ProtectionPilot来统一部署杀毒软件McAfee VirusScan Enterprise 8.5i,进而充分发挥McAfee系列产品的强大安全防护功能,保护整个医院局域网系统的安全。

A Novel Pilot Protection for VSC-HVDC Transmission Lines Based on Correlation Analysis

The control system of voltage source converter HVDC (VSC-HVDC) is complex and its fault tolerance ability is not sufficient, and correct rate of line protection device is not high. A novel pilot protection for VSC-HVDC transmission lines based on correlation analysis is proposed in this paper. In the principle, external fault is equivalent to a positive capacitance model, so the correlation coefficient of the current and voltage derivative is 1;while the internal fault is equivalent to a negative capacitance model, so the correlation coefficient of the current and voltage derivative is -1. Internal faults and external faults can be distinguished by judging the correlation coefficient. Theoretical analysis and PSCAD simulation experiments show that the new principle, which is simple, not affected by transition resistance, control type and line distributed capacitance current, can identify internal faults and external faults reliably and rapidly, having certain practical value.

A new phase comparison pilot protection based on wavelet transform

Current phase comparison based pilot protection had been generally utilized as primary protection of the transmission lines in China from the 1950＇s to the 1980＇ s, Comentional phase comparison pilot protection has a long phase comparison time, which results in a longer fault-clearing time. This paper proposes a new current phase comparison, pilot protection scheme that is based on non-power frequency fauh eun＇ent component. The phase of the fourth harmonic eun＇ent of each end of the protected line has heen abstracted hy utilizing complex wavelet transformation and then compared in order to determine whether the inner fauh occurs or not. This way can greatly deerease fauh-elearing time and improve performances of this pilot protection when fault occurs under the heavy-load current and asymmetrical operation eonditions, Many EMTP simulations have verified the proposed scheme＇s correctness and effectiveness.

Special Problems in Pilot Protections of Transmission Lines Connecting Wind Farms

As the penetration of wind power into power grids increases,higher demands are made on the stability and protection of power systems.Unlike traditional synchronous generators,wind turbines are different on the short-circuit and impedance characteristics,thus some problems exist in pilot protections of transmission lines connecting wind farms.When a single-phase fault occurs on a transmission line,the phase selector based on current-difference sudden-change may mistake the single-phase fault for a phase-to-phase fault.This paper studies the impedance characteristics of an asynchronous wind generator,and analyzes the behavior of a fault phase selector under different conditions.Then,the paper explains that inequality between positive and negative branch coefficients is the cause for the mal-operation of the fault phase selector.Finally,some simulations are done in MATLAB to validate analysis results.

中国男性飞行员体型特征分类

为满足飞行员防护服装的合体性需求,探究了中国男性飞行员的体型特征并对其进行科学分类。选取186位现役中国男性飞行员作为人体测量样本,依照人体测量的质量控制方法进行手工数据采集。经描述统计分析发现,影响中国男性飞行员体型的主要因素集中在围度方面。通过因子分析提取与体型相关的主成分,再借助相关性分析从每个主成分中提取特征变量,并将这些特征变量整合为4种体型指标。随后,运用K-means动态聚类分析对中国男性飞行员体型进行分类。研究结果表明:围度因子和高度因子是影响中国男性飞行员体型形态的主要特征因子,中国男性飞行员体型可分为胖体、瘦体、标准体3类,并依据结果计算得到各类体型中间体。本文研究有助于构建男性飞行员标准人台,为飞行员防护服装的设计和生产提供重要参考。

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。

Energy-Function Based Pilot Protection Scheme for Hybrid UHVDC Transmission Applying Improved Hausdorff Distance

A hybrid UHVDC transmission system applying LCC as the rectifier and MMC as the inverter combines the advantages of both converter types,which makes this protection scheme more complicated.A new pilot protection scheme for a three-terminal hybrid DC transmission system applying energy functions is proposed.The energy function for LCC is applied to MMC to derive the energy level of the hybrid system.Furthermore,an improved Hausdorff distance(IHD)algorithm is proposed to detect the difference in energy levels between the normal and fault states.An abrupt change in energy level is characterized by IHD change rate.Time points at which the IHD change rate exceeds the threshold at converter stations are applied to determine the fault line and to estimate the fault section.The proposed protection scheme is then verified by a simulation model of the Wudongde±800 kV three-terminal hybrid UHVDC transmission project.The appropriate sampling frequency is selected for a real-time calculation,and the threshold is selected considering the effect of noise.Results show the proposed scheme can identify and trip fault lines quickly and effectively,even for a 600Ωgrounding fault.Other waveshape similarity algorithms are compared and analyzed.Compared with existing protection schemes,the proposed scheme transmits less data to improve communication speed and reliability.

Energy-based Directional Pilot Protection for Distribution Networks with IBDGs Considering Unmeasured Load Switching

Inverter-based distributed generations(IBDGs)are the main approach to utilizing clean energy in distribution networks(DNs).Compared with synchronous source,fault response of IBDG is very different.As a result,in DNs with high penetration of IBDGs,legacy protection schemes will no longer be applicable.In this paper,an energy-based directional pilot protection scheme suitabie for DNs with IBDGs is proposed.This scheme considers the large range of phase angle caused by IBDG integration and uses improved energy polarity criterion to determine fault direction.In addition,magnitude of energy is used to distinguish between faults and load switching to overcome maloperation of directional pilot protection caused by internal unmeasured load switching.The proposed scheme first uses local measured information to determine fault direction sign and then exchanges the direction sign with the remote terminal.This scheme does not require high-bandwidth communication and strict data synchronization,so it can be implemented at a low cost.Finally,simulation studies verify effectiveness of the proposed scheme.

Traveling Wave Characteristics Based Pilot Protection Scheme for Hybrid Cascaded HVDC Transmission Line

The hybrid cascaded high-voltage direct current(HVDC)transmission system has various operation modes,and some operation modes have sharply increasing requirements for protection rapidity,while the traditional pilot differential protection(PDP)has poor rapidity,and even refuses to operate when faults occur on the DC line.Therefore,a novel pilot protection scheme based on traveling wave characteristics is proposed.First,the adaptability of the traditional PDP applied in engineering is analyzed for different operation modes.Then,the expressions of the forward traveling wave(FTW)and backward traveling wave(BTW)on the rectifier side and the inverter side are derived for different fault locations.From the theoretical derivation,the difference between the BTW and FTW on the rectifier side is less than zero,and the same is true on the inverter side.However,in the event of an external fault of DC line,the difference between the BTW and FTW at nearfault terminal protection installation point is greater than zero.Therefore,by summing over the product of the difference between BTW and FTW of the rectifier side and that of the inverter side,the fault identification criterion is constructed.The simulation results show that the proposed pilot protection scheme can quickly and reliably identify the short-circuit faults of DC line in different operation modes.

Exploration on MOOC Teaching Pilot College Construction Planning

The spread and innovative application of MOOC in China has rapidly triggered a profound revolution in the curriculum construction and teaching reform of universities,promoting significant results in teaching and talent cultivation.Based on the practice of“MOOC teaching pilot colleges”carried out by the China University Computer Education MOOC Consortium in some universities in China,this paper proposes the overall plan of MOOC teaching pilot colleges construction through the analysis of typical cases,pointing out the purpose and significance of the reform of the pilot college and giving the relevant concepts and requirements.This thesis focuses on the reform of teaching methods,assessment methods,grade calculation and credit recognition,and stress assessment,emphasizing the need for a three-dimensional process management of teachers,students,and college teaching administrators,and the need to focus on institutional development to provide protection.MOOC teaching pilot colleges should reform and innovate in practice,and they should keep solving the problems they encounter and deepen the reform,so as to provide useful experiences and reference practices for the landing and high-quality development of MOOC teaching in more universities.

一种适用于混合双极直流输电的纵联方向保护方法

直流输电线路通常是以大电感和直流滤波器作为边界,故障行波在边界发生折射和反射时,其行波能量也会因为电感和滤波器的存在而被吸收,导致区内、外高频行波能量产生差异.当故障发生为正方向故障时,其高频前行波能量小于高频反行波能量;当故障发生为反方向故障时,其高频前行波能量大于高频反行波能量.由此特征提出了一种基于前、反行波高频能量差异的纵联方向保护,该保护采用小波包变换提取行波的高频能量,利用前行波与反行波在区内故障和区外故障时的高频能量差异判别故障.仿真结果表明,该保护能快速准确地识别故障,并且不受故障类型、过渡电阻以及故障发生位置距离和噪声的影响,具有一定的实用性.

适用于逆变型分布式电源T 接的配电网线路纵联保护方案

针对逆变型分布式电源(IIDG)T接于配电网导致双端电流纵联差动保护难以适用的问题,提出一种基于线路端点正序电流的新型纵联保护方案。建立以并网点正序电压主导的IIDG压控电流源模型。根据线路本端保护测量所得正序电气量分别求解对端正序电流计算值。在此基础上,将同一端点测量值与计算值的相量差幅值作为保护动作量,并利用发生区、内外故障时保护动作量的差异形成故障识别判据。考虑计算误差及互感器传变误差对保护整定值的影响构建完整的保护方案。该方案在保护动作量计算过程中无须实时获取IIDG运行状态,仅在现有双端纵联通道内对线路两端的电气量进行通信即可准确识别区内、外故障,通信压力小。仿真结果表明所提保护方案可靠有效,受IIDG出力影响小且具备一定抗过渡电阻能力。

基于电流模分量特性的多端柔性直流配电网线路纵联保护

多端柔性直流配电网因在供电可靠性方面极具优势而受到广泛的关注,然而对于直流线路保护中故障的快速、可靠识别成为其急速发展所需解决的关键问题之一。因此,设计了一种利用电流模分量特性的直流线路纵联保护方法。该方法利用故障时正极电流线模分量方向来判别区内外故障,以不同故障条件下故障点正极电流零模分量平均值的差异来构造保护判据,从而判别故障类型,形成保护策略。最后,在PSCAD/EMTDC4.5上搭建了多端柔性直流配电网模型,对保护判据及关键影响要素进行了仿真分析。结果表明,该保护方法能够有选择性地快速、可靠识别区内外故障及故障类型,且具有较好的耐过渡电阻与抗噪声能力。

适用于双馈风电场送出线的纵联方向保护研究

考虑风电场接入电网时,传统方向元件在短路故障发生时易受到风电场内部电力电子器件动态特性的干扰影响,导致频率特性偏移,系统参数不稳定和弱馈性等问题,使继电保护装置不能及时或正确判断故障发生区域。针对上述问题,首先对含有风电场的故障附加网络进行分析,寻找故障发生后纵联保护安装处各测量点电气量之间的关联性,确定其故障逻辑关系。其次通过对常用的相模变换解耦方式进行分析,选择一个合理的方法代入相关性表达式,根据相关系数值完成故障区域判定。最后利用PSCAD/EMTDC搭建双馈风电场并网模型,设置各种不同的故障类型和场景,并利用Matlab进行保护算法验证,检验故障区域判断结果,验证所提保护方法的正确性与合理性,并且仿真结果表明该方法具有较高的可靠性。

特勒根似功率保护在同塔双回交流输电线路中的应用

随着我国电网规模快速扩张,输电通道资源日渐紧缺,同塔多回输电技术逐渐得到广泛应用。超/特高压远距离输电线路一般以差动保护作为双重主保护,与纵联距离/方向保护构成双重化配置。但用于同塔双回输电线路时,分布电容电流将影响差动保护的灵敏度;同时,由于双回线线间和相间较强的电磁耦合作用,线间互感的影响将会降低纵联距离、纵联方向保护判断的正确性,导致原来的保护配置方案难以直接应用。将特勒根似功率保护原理推广至同塔双回线路,提出了一种基于特勒根似功率定理的同塔双回输电线路纵联保护方法,能够不受双回线内部复杂电磁耦合、分布电容、系统负荷等影响,并验证了该保护的对时方案在双回线路中的适用性。采用MATLAB/Simulink仿真软件搭建1000kV特高压同塔双回输电线示范工程模型,经大量仿真实验,验证了所提保护方法的有效性。

基于扩展边界的柔性直流输电网区域纵联保护

直流保护是保证多端柔性直流输电网安全的关键。行波保护动作速度快,可满足现有柔直电网对保护速动性的要求,但存在采样频率较高、可靠性不足、在线路边界受限时灵敏性较低的问题。针对上述问题,充分利用换流站及其各出线上的平波电抗器组成扩展边界,提出新型区域纵联方向保护原理。首先,分析扩展边界两侧电压的故障特征,利用扩展边界对电压时域波形的显著衰减形成的正反方向不同的故障特征来构造方向元件,构成纵联方向保护。该保护原理同时具备母线故障判别能力,并与相邻保护协调配合形成区域保护方案。其次,分析行波多次折反射过程对方向元件的影响,并给出保护动作时间。最后,进行仿真分析和对比验证。所提保护原理对采样频率要求低,在高阻故障、强噪声以及边界特性削弱时仍具有较高的灵敏性和可靠性。

基于电压-电流采样轨迹的混合直流输电线路纵联保护方法

为提高混合直流输电系统线路保护的抗干扰能力和适用范围,提出一种基于电压-电流采样轨迹的直流输电线路保护方案。首先,从理论上分析了直流线路故障时测量电压与测量电流之间的关系,揭示了区内/外故障时的电压-电流线性度差异。然后,以区外故障时电压-电流所服从的线性模型作为假设模型,将实测数据得到的采样轨迹与假设模型对应的直线进行比对,引入拟合优度指标作为特征量来量化并放大实测数据与假设模型的差异,并进一步给出直流输电线路保护方案。最后,在PSCAD/EMTDC中建模并仿真分析了多种因素对所提保护方案的影响,结果表明所提保护方案能够可靠、快速地识别直流输电线路故障,在高阻和强噪声的场景下仍可适用,且无需提取特征频带,无需双端数据严格同步,对于保护装置的采样率要求较低,易实现工程应用。

基于5G的高风光渗透率型配电网相关性纵联保护

在高风光渗透率型配电网中,受逆变器控制策略的影响,故障电流弱馈特征明显,传统工频电气量保护动作性能下降,甚至出现误拒动。文章分析了同步发电机和逆变型分布式电源的故障电流特征,获知配电网区内、外故障时两侧故障电流向量存在明显差异,进而提出利用相关系数度量向量相关性并构造动作判据,基于5G通信技术提出高风光渗透率型配电网相关性纵联保护新方案。仿真结果表明,所提保护方案能够快速、稳定地判别高风光渗透率型配电网线路短路故障,有较强的耐噪声能力,解决了5G时延波动对纵联保护的影响。

基于状态估计的大规模新能源送出线路纵联保护

“双碳”背景下,加快构建清洁低碳、安全高效的能源体系,已成为国家重大需求。但是,新能源电源等值内电势不稳定,与传统同步机电源特性存在本质差异,换流器控制导致故障电流幅值受限、相位受控,现有工频量保护性能下降,威胁电网安全稳定。该文提出基于状态估计的大规模新能源送出线路纵联保护原理,在考虑线路分布电容的基础上建立精确的线路模型,利用瞬时值的状态估计冗余特性提升了保护的速动性和可靠性,通过比较所建模型与实际模型匹配程度判别故障。仿真表明,所提保护方法能快速可靠判别各种类型的区内、外故障,保护判别时间不超过2ms,并具有较好的耐过渡电阻和抗干扰能力。

基于差动电流与分布电容电流比值的直流线路纵联保护方案

分布电容电流会对直流线路纵联保护性能造成影响。文中以三端混合高压直流输电线路为对象,讨论分析了差动电流与分布电容电流比值的故障特征。由于差动电流和分布电容电流都会随着过渡电阻的增大而减小,采用差动电流与分布电容电流的比值作为判据,可以削弱过渡电阻对判据的影响,提高保护的灵敏性。基于此,提出了一种基于差动电流与分布电容电流比值的纵联保护方法。基于PSCAD/EMTDC的仿真验证表明,所提保护判据整定简单且天然具有故障选极功能,能可靠识别区内外故障,耐过渡电阻能力强且具有较高的灵敏性和可靠性。