【作者】 邹贵彬；

【导师】 高厚磊；

【作者基本信息】 山东大学 ， 电力系统及其自动化， 2009， 博士

【摘要】 随着我国对电力负荷需求的强劲增长,西电东送、南北互供、全国联网工程的实施,一个超大规模互联电网正逐步形成。大容量远距离输电、大规模互联电网的安全保障和防御体系是电力工作者当前面临的新挑战。作为骨干网架的超、特高压输电线路,对继电保护的快速性、可靠性和灵敏性等指标提出了更高的要求。在基于工频量的继电保护其动作速度已接近极限的情况下,行波保护由于具有极快的故障检测能力而备受关注,但其低可靠性的缺点始终制约着保护装置的研发。为此,本课题旨在保持行波保护快速的故障检测能力的同时,提出了一种高可靠性的积分型行波方向保护原理并围绕该原理保护进行了相关技术的研究。论文所做主要工作如下:(1)提出了一种积分型行波方向保护判据。该原理判据利用故障发生后正反向行波在一定时间内的恒定关系,构造积分判据,并以二者比值大小作为识别故障方向的依据。500kV和1000kV两种电压等级的仿真数据表明该原理保护能够适用任何线路或母线结构,故障初始条件对保护判据的性能几乎没有任何影响,解决了只利用初始行波波头的极性或幅值关系而导致传统行波方向保护低可靠性和灵敏度不足问题。对于中短距离的输电线路,保护具有极快的故障方向判别速度。而对于远距离的输电线路,由于积分窗口的加大,判别速度有所降低。分析表明对于远距离输电线,可通过调整积分时间,提高判别速度。仿真结果验证了利用一半的时间窗,保护判据的性能不受影响。(2)在分析雷击未造成故障、雷击造成故障和一般短路故障暂态波形特征的基础上,提出了一种基于暂态电流波形积分的雷击干扰与故障的识别判据。针对不同的雷击情形和故障条件,仿真分析表明该判据能够快速、正确地识别雷击干扰和短路故障,是一种简单、易行的识别方法。另外,论文分析了断路器合闸和分闸操作产生行波信号的机理,并根据高压输电线路电压互感器一般安装于线路侧的现状,提出可利用积分型行波幅值比较式方向判据对扰动源的方向进行判别。对开关操作的仿真结果表明,积分型方向识别判据能够正确判定开关操作的方向。(3)针对电容式电压互感器(CVT)不能有效传变暂态高频电压信号的缺陷,利用CVT套管末屏电容设计出串、并联谐振回路,进而提取电压行波信号。利用仿真模型检验了提取电路对不同频率信号、不同故障接地电阻、不同故障初始角的输出响应。理论分析和仿真结果表明该方法能够有效地抑制工频分量,正确地反应暂态电压行波信号,解决了行波保护和行波故障定位中电压行波信号提取的技术难题。(4)基于以上研究,设计了一套积分型行波方向纵联保护的构成方案。对方案中的重要组成部分,如启动元件、故障选相元件、故障方向判别元件、主判据、雷击和开关操作识别以及通信通道的选择等,进行了理论分析和部分仿真。理论分析和仿真数据表明:本文所提出的积分型行波方向保护原理不受故障初始条件的影响,对线路长度和母线结构有较好的适应性,极大的提高了行波方向保护的鲁棒性、可靠性和灵敏性;所提雷击干扰与故障信号的识别判据能够正确判别各种非故障性雷击干扰;积分型行波方向判据能够正确识别开关操作;所设计的电压行波提取电路能够正确有效的提取故障暂态电压行波信号。更多还原

【Abstract】 With the rapid growth of power load,power transmitted from western district to eastern district,power supplied by south and north mutual and implementing of power grid interlink project,an extra-huge scale power grid is forming gradually. For the staffs engaging in power field,the safity and stability of power transmitting with high capacity and remote distance in a huge scale power grid is a challenge.For extra / ultra high voltage transmission lines,the protective relay should has a more excellent performance,such as operation speed,reliability and sensitivity and so on. In the condition of operation speed approaching limit of the relay based on power frequency,travelling wave protections had been focused on owing to it has an ability of finding fault rapidly,but the shortcoming of lower reliability had always restricted development of device.Therefore,a high reliable travelling wave directional protection scheme is proposed,as well as retaining the ability of detecting fault rapidly.In the studying process,main results obtained are following:(1) A novel integral based travelling wave directional protection is proposed.After fault occurred,using the constant relationship of forward and backward travelling wave during a special period,the waveforms of forward and backward travelling wave are integrated respectively.According to their ratio,the direction of fault is discriminated.Simulation results from 500kV and 1000kV transmission lines show that the presented directional criterion can completely adapt any constructions of line or busbar,and conditions of fault do not have any influence on performances of criterion.Therefore,the lower reliability and sensibility of traditional travelling wave protection only detecting the polarity or complitude of initial travelling wave are solved.In addition,for these transmission lines of medium or short distance, protection has quick discrimination speed of fault direction.For long distance transmission lines,as a long integral window,discrimination speed is relative slow. Analysis verifies,for the romote distance lines,that discrimination speed can be improved through adjusting time-window(such as using half integral time). Simultaion results clarify protective criterion has not been affected using half integral time. (2) On the basis of analyzing transient waveform characteristics of lightning stroke without leading to fault,lightning stroke with resulting in fault and general short-circuit fault,a discrimination criterion of lightning stroke and fault based on waveform integral of current travelling wave is proposed.For different lightning strokes and faults,lots of simulations have been carried out.Simulation and analysis demonstrate that the criterion can quickly and correctly determined fault or lightning stroke,and it is a simple and liable discrimination method.In addition,the paper analyzes mechanism of travelling wave generated by breaker switching.According to the fact of PT located at the side of line in high voltage transmission system,a method determining direction of disturbance is proposed using the integral based travelling wave amplitude comparison directional criterion,at the same time, simulation of breaker switching is carried out.Simulation results verify that the criterion can accurately discriminate the direction of disturbance source.(3) Aming at the shortcoming that CVT can not effectively transduce transient high frequency signals,a method extracting voltage travelling wave signal is proposed.Using tap capacitance of capacitance transducer,series and shunt resonance circuit is designed.Using simulation model,output responses of extraction circuit to different frequency signals and different fault ground resistances and different fault inception angles are checked and analyzed respectively.Theoretic analysis and simulation results demonstrate that the method can effectively restrain power frequency signals,accurately reflect transient voltage travelling wave signals, and thus solve technical problem extracting voltage travelling wave for travelling wave protection.(4) A set of integral based travelling wave directional unit protection scheme is designed.The main components,such as fault start-up component,faulted phase selection component,fault direction discrimination component and lightning stroke and breaker switching and so on,are analyzed and simulated.Analysis of principle and simulation results demonstrate that the integral criterion do not be affected by conditions of fault and for the length and structure of line,it has a good applicability;the applicability and reliability and sensibility of travelling directional protection are enormously improved;lightning stroke criterion can accurately discriminate general line fault from other disturbances;direction of various breaker switching can also be correctly determined by integral critertion and the designed circuit can obtain transient voltage travelling wave correctly and effectively.更多还原