NEW PRINCIPLE FOR DIRECTIONAL COMPARISON CARRIER PROTECTION OF EHV TRANSMISSION LINES

The increasing scale and complexity of power systems require high performance and high reliability of power system protection.Protective relaying based on directional comparison with power line carrier or microwave channels is the most suitable protection scheme for long distance EHV transmission lines and is widely used in power systems.The key element of such protection is a directional relay used to discriminate the fault direction.In order to overcome the disadvantages of conventional directional relays,the authors of this paper put forward the directional comparison carrier protection based on the artificial neural network(ANN).The protection is extensively tested using electromagnetic transient program (EMTP) under various electric power system operating and fault conditions.It is proved that the directional comparison carrier protection based on ANN,which can recognize various fault patterns of the protected transmission line(such as fault direction,fault phases etc.)correctly in any kind of operating and fault conditions and the whole process,is satisfactory for EHV transmission line protection.

基于序电流相位差的EHV/UHV输电线路高阻抗故障选相研究

为了实现超高压和特高压输电线路的故障快速诊断,将序电流相位差技术应用到输电线路高阻抗故障选相中。开展了三相网络单相接地故障和相间接地故障分析,通过零序和负序电流分量相位差对故障相区间进行了划分,建立了序电流相位差、相阻抗、相间阻抗、3段距离继电器保护范围与故障类型、故障相别的关系;提出了一种以序电流相位差为判断依据的超高压和特高压输电线路高阻抗故障选相新方法;在500 kV,400 km的输电线路上对该故障选相方案的精确性及可靠性进行了评价,并进行了RTDS仿真测试。研究结果表明:该故障选相方案能够实现精确可靠的识别,并有足够的边际应对意外因素或计算误差,即使在电网振荡时,也可以实现可靠的系统故障相识别。

基于暂态电流信号的EHV输电线路保护新方案

提出了一种基于单端电流暂态信号小波变换的超高压输电线路快速保护方案。利用单端暂态电流信号的小波变换模极大值,对电流信号的李氏指数进行最小二乘法估计,来判断故障线路。通过大量ATP仿真证明,在各种故障情况下该保护算法能准确、可靠地动作。

A review of single phase adaptive auto-reclosing schemes for EHV transmission lines

Statistics shows that transients produced by lightning or momentary links with external objects, have produced more than 80% of faults in overhead lines. Reclosing of circuit breaker (CB) after a pre-defined dead time is very common however reclosing onto permanent faults may damage the power system stability and aggravate severe damage to the system. Thus, adaptive single-phase auto-reclosing (ASPAR) based on investigating existing electrical signals has fascinated engineers and researchers. An ASPAR blocks CB reclosing onto permanent faults and allows reclosing permission once secondary arc is quenched. To address the subject, there have been many ASPARs techniques proposed based on the features trapped in a faulty phase. This paper presents a critical survey of adaptive auto-reclosing schemes that have hitherto been applied to EHV transmission lines.

Analysis of the Behavior of a HV AC Line during an Atmospheric Discharge and Evaluation of the Spatio-Temporal Distribution of the Lightning Current Wave

In high voltage networks for the transport of electrical energy, lightning, a phenomenon as dangerous as it is impressive, with an easily recognizable form, can affect a power line by striking either a phase conductor, a tower or a guard cable, thus causing more dangerous and constraining stresses on the lines for its proper operation. Thus, this article aims to analyze the behavior of a HV line during an atmospheric discharge and assess the spatial and temporal distribution of the lightning current wave. For this purpose, the generalities on the transmissible power in case of link without resistance and the modeling of the atmospheric surge propagation established on the basis of the theory of the lines with distributed constants implementing the wave equation known as the Alembert equation have been developed. Through this research, we are interested in the study of the space-time distribution of the lightning current wave in order to model the radiated electromagnetic field and to examine the influence of the atmospheric discharge induced overvoltage on the transportable power of a High Voltage AC Transmission line, for a good selective protection in order to illuminate the parasites. The 2D simulation based on engineering and “Transmission Line” models have been developed as well as the verification of the coherence of the different models, by comparing the fractal dimensions of the program results with those of the experimentally obtained figures.

Fault component integrated impedance-based pilot protection scheme for EHV/UHV transmission line with thyristor controlled series capacitor(TCSC) and controllable shunt reactor(CSR)

This paper analyzes the fundamental frequency impedance presents a novel transmission line pilot protection scheme characteristic of a thyristor controlled series capacitor （TCSC） and based on fault component integrated impedance （FCII） calculated for a transmission line with TCSC and controllable shunt reactor （CSR）. The FCII is defined as the ratio of the sum of the fault component voltage phasors of a transmission line with TCSC and CSR to the sum of the fault component current phasors where all the phasors are determined at both line＇s terminals. It can be used to distinguish internal faults occurring on the line from external ones. If the fault is an external one the FCII reflects the line＇s capacitive impedance and has large value. If the fault is an internal one on the line the FCII reflects the impedance of the equivalent system and the line and is relatively small. The new pilot protection scheme can be easily set and has the fault phase selection ability and also it is not affected by the capacitive current and the fault transition resistance. It is not sensitive to compensation level and dynamics of TCSC and CSR. The effectiveness of the new scheme is validated against data obtained in ATP simulations and Northwest China 750 kV Project.

Corona Onset Voltage Gradient of Bundle Conductors for EHV/UHV AC Power Lines in Corona Cages Considering Altitude Correction

The corona onset voltage gradient(COG)of conductors is a key parameter in the design of overhead transmission lines.The commonly used semi-empirical calculation formula proposed by Peek(1910s)at present can roughly estimate the COG of single conductors and is not applicable to large cross-section bundle conductors.In this paper,experiments are conducted to investigate the corona characteristics of a whole series of bundle conductors at different altitudes,and a prediction formula is proposed for the COG of large cross-section bundle conductors on AC transmission lines considering the altitude correction.The calculated values using the proposed prediction formula are compared with the experimental values of the COG in two cases:UHV eight-bundle conductors at an altitude of 19 m;500 kV UHV four-bundle conductors in Wuhan,Xining,Geermu,and Nachitai at four different altitudes.The results show that the use of the formula can predict the COG of bundle conductors with the radius of 1.34 cm to 1.995 cm and the number of subconductors of 4 to 12 at altitudes of 19 m to 4000 m above the mean sea level.The research findings can provide a reference for the design of EHV and UHV overhead transmission lines and even those in higher voltage levels.

PMU based adaptive zone settings of distance relays for protection of multi-terminal transmission lines

This paper proposes Phasor Measurement Unit(PMU)based adaptive zone settings of distance relays(PAZSD)methodology for protection of multi-terminal transmission lines(MTL).The PAZSD methodology employs current coefficients to adjust the zone settings of the relays during infeed situation.These coefficients are calculated in phasor data concentrator(PDC)at system protection center(SPC)using the current phasors obtained from PMUs.The functioning of the distance relays during infeed condition with and without the proposed methodology has been illustrated through a four-bus model implemented in PSCAD/EMTDC environment.Further,the performance of the proposed methodology has been validated in real-time,on a laboratory prototype of Extra High Voltage multi-terminal transmission lines(EHV MTL).The phasors are estimated in PMUs using NI cRIO-9063 chassis embedded with data acquisition sensors in conjunction with LabVIEW software.The simulation and hardware results prove the efficacy of the proposed methodology in enhancing the performance and reliability of conventional distance protection system in real-time EHV MTLs.

基于MATLAB的电力系统短路故障仿真分析

超高压输电线路和电力供配电系统对电力系统的安全稳定运行影响极大。设计使用MATLAB/Simulink电力系统工具箱搭建超高压输电线路和无限大功率供配电系统仿真模型,在仿真模型下对系统发生三相短路和不对称短路故障时的故障特征量以及出现的序分量特征量进行分析,仿真结果验证了系统模型的正确性,可以作为系统发生短路故障分析的依据。

超、特高压交直流输电线路可听噪声研究综述

近年来架空线路可听噪声逐渐成为限制输电线路建设的重要电磁环境问题。为此总结了交直流输电线路可听噪声研究现状,包括可听噪声的产生机理、测量以及评估,着重分析了直流线路与交流的主要区别和研究难点。结果表明目前对于可听噪声的研究已经取得了一定进展,但是交直流线路电晕效应之间存在较大差异且认识不足,造成这些差异的主要原因是直流线路离子电场的影响;分析表明未来仍然可以利用电晕笼研究直流线路的电晕效应,关键在于建立电晕笼与实际线路在合成电场上的关联。

超高分子聚乙烯绳索在封网跨越施工中的应用

高性能的封网用绳索是输电线路封网带电跨越施工安全可靠的关键问题,但现有封网用迪尼玛绳难以适应超特高压输电线路带电跨越的大尺寸、长距离和重荷载等安全条件要求。这里结合输电线路带电跨越用封网的基本功能,考虑封网用绳索力学性能及其电气净空距离需求,提出了一种基于超高分子聚乙烯绳索的超高压输电线路封网带电跨越技术。通过构建封网承载索的力学计算模型,推导了空载状态、安全放线状态、静载事故状态和动载事故状态下,承载索的水平张力及其电气净空距离求解公式。同时,通过拉伸实验的方法,获取了超高分子聚乙烯绳索的破坏张力。计算与实验结果表明,采用同规格的超高分子聚乙烯绳索可使施工安全系数增加(13~20)%,单位重量降低(6~15)%,同时可在一定程度上增加封网的净空距离。经500kV博贺电厂送出工程阳江段带电跨越220kV蝶旗甲线实操应用,超高分析聚乙烯绳索能够满足大尺寸、重荷载跨越带电线路施工条件下的封网防护任务,证明了绳索的优越性。

直升机吊篮法带电作业在三峡高海拔山区±800 kV特高压直流输电线路中的应用

随着直升机带电作业体系逐步完善及马鞍式吊篮设计逐渐成熟,直升机吊篮法带电作业相较于平台法及吊索法在安全性、适用性及便捷性等方面优势正逐步凸显。三峡高海拔山区特高压输电线路具有交通不便、作业环境恶劣等特点,开展常规带电作业方式其劳动强度大、质效较低。以±800 kV祁韶特高压直流直升机吊篮法带电作业缺陷处置过程为例,分析作业侵入路径、安全距离及其他关键安全技术措施,在施工效率、安全裕度等方面与传统带电作业方式开展比对。分析直升机吊篮法带电作业在三峡高海拔山区运用的优缺点,探索后期规模化应用可行性及质效提升。

输电线路雷电过电压的影响因素分析

随着我国工业水平的不断进步,整体的经济水平全面提升。在电力系统中超高压电网相关的技术水平也随之不断改进和提升,尤其是目前我国供电行业的超高压输电线路的传输距离、高度等都在全面提升。近几年,同塔双回输电技术在国内得到了广泛的应用,其总体设计、制造、施工等方面都比较成熟。然而,当前在电力传输过程中,由于雷击引起的电力系统故障仍时有发生,因此有关方面的专家必须对雷击过电压的瞬变特性、输电线路的抗雷性等问题进行深入的研究。同时,采用计算机仿真软件,对电网中的雷电过电压的影响因素进行了科学的分析,并采用合理的模拟方法,探讨了相应的规律,从而对以后的输电线路的防雷设计具有十分重要的参考意义。

南方区域超、特高压输电线路耐张引流板发热原因分析及对策

针对南方区域迎峰度夏期间超、特高压输电线路不同程度出现耐张线夹引流板和引流线夹过热现象,笔者通过分析发热产生的条件,查找发热产生的原因,得出设备本身质量缺陷、螺栓松动、施工工艺不满足要求、采用劣质电力复合脂及接触面腐蚀是发热的主要原因,并针对发热的原因提出相应的处理措施。经工程应用验证,所提出的措施可有效降低耐张引流板发热缺陷,对提高电力系统稳定性具有重大意义。

直流融冰技术在超高压输电线路中的相关应用分析

线路覆冰是影响超高压输电线路正常运行的一个关键问题,也是致使电力系统出现故障的原因之一,为此,就需要通过有效的手段与方式,做好超高压输电线路的融冰工作.当前直流融冰是一种应用效果较好的融冰技术.文章主要分析直流融冰技术的相关特点以及在超高压输电线路中的相关应用,以供参考.

同塔双回超高压输电线路绕击耐雷性能影响因素分析

超高压(Extra High Voltage,EHV)输电线路多为同塔双回,引雷面积大,更易遭受到雷击,特别是对于山谷间大跨度的杆塔常发生绕击跳闸事故。据运检单位统计表明,绕击是引起线路跳闸的主要原因。因此,对输电线路雷电绕击进行分析,探讨影响同塔双回输电线路防雷性能的敏感因素是十分必要的。建立500 kV输电线路的绕击模型,该模型采用电气几何模型(Electrical Geometric Model,EGM)法,通过呼高、地面坡度、保护角、导线相序排列变化所导致的雷电绕击跳闸次数变化来反映出各因素对于绕击耐雷性能的影响。

超高压输电线路风偏故障原因分析

超高压输电线路所处地理环境复杂,极易受到风、覆冰等自然因素的影响,特别是强风天气下可能会发生风偏闪络故障,对输电线路的安全稳定运行造成极大的威胁。该文针对湖北省发生的一起500 kV输电线路风偏闪络故障,通过对输电铁塔结构、天气实际数据及现场故障状况进行分析,总结故障发生的原因,为线路整改措施制定提供参考。经计算该线路绝缘子串在原设计气象条件下实际摇摆角为53.3°,小于允许摇摆角54.58°,而在故障期间短时风速31.8 m/s下的风偏角超过允许摇摆角,导致电气间隙不满足安全距离,产生风偏放电现象。

南方区域输电线路风偏故障原因及防范策略分析

近几年来,南方区域台风频发,对输电线路的安全稳定运行造成重大威胁。为降低风偏故障发生概率,笔者通过分析超高压输电线路发生风偏故障的原因,总结出风偏故障的规律和特点,并提出加装重锤片、加装防风拉线、缩短线路档距、采用复合横担塔等措施。部分措施已在实际输电线路中得到应用,加装重锤片或缩短线路档距后至今未发生风偏故障。该文所提出的措施可为后续处理输电线路风偏故障提供借鉴。

高压输电线路紫外在线检测系统

介绍了一种基于紫外线检测的放电在线检测系统,该系统克服了过去红外检测、超声波检测和泄漏电流检测法的不足。高压设备放电会产生微弱的紫外线,其中有小部分波长在日盲区(240nm-280nm)内,可避开日光中紫外线的干扰。利用日盲型的紫外传感器,可以通过检测特定波长的紫外线来正确检测高压设备的放电。为了检测紫外检测器的放电检测效果,制造了2种不同的紫外检测器驱动电路板,并比较了输出波形。实验发现,2种电路板都可以对10m内的放电火花正确反应,放电检测能力可通过电源电压调整,并且不受外部环境影响。

高压架空输电线路的故障测距方法

对高压架空输电线路进行准确的故障测距是保证电力系统安全稳定运行的有效途径之一。为此 ,文章比较全面地介绍了国内外在此方面的发展历程和研究现状。根据各测距算法采用的原理不同 ,将现有的各种测距算法分为行波测距、单端测距和双端测距三类 ,然后逐类对各种算法的理论基础和应用条件上进行了分析、对比和讨论 ,并在此基础上总结得出了各测距算法的优点及存在的问题 ,指出了每种测距算法的适用范围和应用局限性。最后 。