高压直流输电线路保护与故障测距原理研究

发布时间：2018-03-30 22:04

本文选题：高压直流　切入点：输电线路　出处：《山东大学》2014年博士论文

【摘要】：直流输电线路保护和故障测距是直流输电工程保护系统的重要组成部分,担负着快速检测和清除线路故障的任务,其运行性能将直接影响直流输电系统和电网的安全运行。统计研究表明直流输电线路已成为直流输电系统中故障率最高的元件,而直流输电线路保护的正确动作率只有50%。我国直流输电工程的发展位于世界前列,但对现有直流输电线路保护与故障测距装置核心技术的掌握仍然不足,缺乏系统的理论支持,已投运直流输电工程的保护系统大多采用ABB和SIEMENS两家公司的技术路线。提高我国高压直流输电线路保护与故障测距的理论水平和加快直流保护系统的自主研发势在必行。现己投运的直流输电线路主保护易受雷电、换相失败等暂态过程的干扰,耐受过渡电阻能力有限,判据门槛值整定计算复杂。国内外学者致力于对现有直流输电线路主保护进行改进或提出新型主保护原理,其中部分保护新原理存在理论不完备、保护判据所用信号能量小、对装置采样率要求高、缺乏整定依据或整定计算依赖仿真结果等问题。高压直流输电线路故障测距所采用的原理可分为行波法和故障分析法。目前运行中的直流输电线路故障测距装置均采用行波原理,行波故障测距的可靠性在高阻接地故障和波头识别失败时受限。基于故障分析法的故障测距原理性能稳定,故障测距精度一般没有行波法高,部分原理耐受过渡电阻能力有限。全面深入的高压直流输电系统故障暂态分析可为直流输电线路保护与故障测距原理的研究工作奠定基础。本文研究了高压直流输电系统故障暂态特性分析需要考虑的影响因素,深入分析了相应影响机理,给出了仿真案例实现方案,并对直流线路电气量的暂态特征进行分析；提出了耐受过渡电阻能力强、判据门槛值整定不依赖于仿真计算的高压直流输电线路主保护原理和可靠性良好、测距精度高、耐受过渡电阻能力强的直流输电线路双端行波故障测距新算法。主要研究内容及结论如下： (1)高压直流输电系统故障暂态特性研究。现有直流输电系统故障暂态分析相关内容大多作为线路保护与故障测距研究的考虑因素出现在文献的理论分析和仿真验证中,受文献篇幅和考查内容所限。本文从直流输电线路保护与故障测距角度出发,开展了较为全面的高压直流输电系统故障暂态特性分析。对直流输电系统的基本控制原理和控制系统的分层结构进行研究,分析了控制系统对故障暂态的响应时间和电气量的故障稳态值；研究了两端双极直流输电系统多种可能运行方式的运行条件与控制策略,并对不同故障前运行方式下直流线路故障电压电流的暂态特征进行了对比分析；分析了直流滤波环节的阻抗特性及其对故障后暂态过程的影响,提出在直流输电线路故障暂态电压电流信号的低频带特征分析中,可将直流滤波器和平波电抗器视为固定阻抗；分析了故障类型、故障位置和过渡电阻值对直流线路故障电压电流暂态特征的影响；研究直流输电线路的雷电放电计算模型,给出了雷击暂态仿真中雷电流源、杆塔模型、绝缘子闪络模型和输电线路模型的仿真建模方法,对故障性雷击和雷击干扰下直流线路电压电流的暂态特征进行了分析；研究了直流输电系统换相失败的形成机理、判断标准和单双极换相失败的仿真方法,分析了换相失败情况下直流线路电压电流的暂态特征。以上工作可为后续高压直流输电系统故障暂态分析研究提供直接有效的参考,为直流输电线路保护与故障测距原理研究奠定基础。 (2)考虑故障选极的高压直流输电线路保护原理研究。分析了故障后直流输电线路电压突变量的暂态幅值特征,发现故障极线路的电压突变量幅值大于健全极,且电压突变量的积分值能够更好地体现这一特征；提出了利用两极线路电压突变量积分值的比值构造的故障选极判据,给出了判据门槛值整定方法；分析了故障后直流输电线路电流突变量的暂态极性特征,发现故障极线路两端电流突变量的极性在区内故障时相反,在区外故障时相同；提出了利用故障极线路两端电流突变量极性构造的区内故障判据,并采用平稳小波变换提取电流突变量的极性。由此构成的高压直流输电线路主保护满足选择性和速动性的要求,判据门槛值整定方法简洁且不依赖于仿真计算；在10kHz及以上的采样频率范围内均可实现；只需对端电流突变量的极性信息,对通信通道的可靠性要求较低,尤其适用于需要选择故障极的情况。基于中国银东±660kV直流输电工程的实际参数,本文建立了±660kV高压直流输电系统的PSCAD仿真模型,利用仿真数据验证了考虑故障选极的高压直流输电线路保护原理在不同故障情况下的动作特性。仿真结果表明,该保护原理在两端双极直流输电系统的多种运行方式下能够快速选出故障极和判别直流输电线路保护区内故障,耐受过渡电阻能力强,可实现高压直流输电线路的全线速动保护。 (3)基于电压和电流突变量方向的高压直流输电线路保护原理研究。考虑故障选极的直流输电线路保护一般在极-极故障这一罕有情况发生时不能正确工作,因此,本文提出了直接判别直流线路保护区内故障的直流输电线路保护原理。对故障后直流线路电压和电流突变量的暂态特征分析发现,直流输电线路两端电压和电流突变量的方向在直流输电线路保护区内故障和区外故障时不同；通过将电压和电流突变量在一段时间内的积分值与设定门槛值比较,提出了电压和电流突变量的方向判据；通过比较线路两端电压和电流突变量的方向,提出了基于电压和电流突变量方向的高压直流输电线路保护原理。该保护原理的判据门槛值整定不依赖于仿真计算；仅利用线路两端电压和电流突变量的方向信息便可准确识别直流输电线路保护区内故障,对通信通道的可靠性要求不高；不需要进行采样数据同步处理；电压和电流突变量方向判据仅计算5ms数据窗内的积分值,对数据计算速度和采样频率要求较低,采样频率为10kHz及以上时即可满足保护判据计算要求。利用±660kV高压直流输电系统的PSCAD仿真数据对该保护原理在不同故障情况下的动作特性进行了验证。该保护原理在直流线路保护区内故障性雷击、高阻接地故障和极-极故障时能准确动作,在雷击干扰和线路保护区外故障等情况下不误动,能实现直流输电线路的全线准确速动保护,适用于双极直流输电系统的多种运行方式,实用性强。 (4)高压直流输电线路双端行波故障测距新算法研究。分析了故障行波在直流输电线路上的传播特点,发现可用行波波头传播特性曲线表征故障行波在线路上的传播过程,联立直流输电线路本端和对端的行波波头传播特性曲线可计算出故障位置。本文通过检测沿线分布电流的初次突变时刻求出线路两端的行波波头传播特性曲线,提出了直流输电线路双端行波故障测距新算法及其实现策略。该故障测距算法无需另外增加测量点,对通道的可靠性要求不高,算法数据窗口短,可不受控制系统调整的影响。基于PSCAD的仿真结果表明,本文故障测距算法在两端双极直流输电系统的多种可能运行方式下,在线路全长范围内均能实现准确测距,故障点靠近线路中点时测距准确度升高,测距精度不受过渡电阻值和直流线路出口故障的影响,最大故障测距误差约为线路全长的0.1129%。相较于现有高压直流输电工程中应用的双端行波故障测距,虽然本文故障测距算法的计算过程较为复杂,但是其可靠性、抗干扰能力和耐受过渡电阻能力有显著提高,而故障测距误差与之基本相同,保留了行波故障测距原理定位精度高的优点。因此,本文故障测距算法可作为现有直流输电线路双端行波故障测距的有效补充。本文研究内容及成果对提高直流输电线路保护与故障测距理论水平有重要学术价值,可为构建快速可靠的直流保护系统、加快直流系统故障恢复速度和保护设备的自主研发等提供理论支持,选题具有工程实用意义。
[Abstract]:DC transmission line protection and fault distance measurement is an important part of DC transmission project protection system . The operation performance of DC transmission line is the highest in DC power transmission system , and its operation performance will directly affect the safe operation of DC power transmission system and power grid . The statistical study shows that DC transmission line has become the highest fault rate in DC transmission system , and the correct operation rate of DC transmission line protection is only 50 % .

The main protection of HVDC transmission line is easy to be disturbed by the transient processes such as lightning , failure of phase change and so on . It has limited ability to withstand transient resistance and complicated calculation of threshold value . The principle of fault distance measurement of HVDC transmission line is limited . The fault location principle of HVDC transmission line is limited . The fault location principle of HVDC transmission line is stable . The fault location accuracy is generally not high , and partial principle is limited to the ability of transient resistance .

The transient analysis of high voltage direct current power transmission system can provide the foundation for the research of DC transmission line protection and fault location principle . In this paper , the influence factors of transient characteristic analysis of HVDC transmission system are studied , the corresponding influence mechanism is deeply analyzed , the simulation case realization scheme is given , and the transient characteristics of the electrical quantity of DC line are analyzed .
In this paper , the new algorithm of double - end travelling wave fault location based on high voltage direct current transmission line with strong capability of resisting transient resistance is put forward , which is not dependent on the main protection principle and reliability of high voltage direct current transmission line with high reliability , high precision and high resistance to transition resistance . The main research contents and conclusions are as follows :

( 1 ) Study on transient characteristics of HVDC system fault .

In this paper , the analysis of the transient characteristics of HVDC transmission system is carried out based on the protection and fault location of DC transmission line . The basic control principle of HVDC transmission system and the layered structure of control system are studied , and the response time of the control system to fault transient and the fault steady state value of electric quantity are analyzed .
The operating conditions and control strategies of a variety of possible operating modes of the two - pole HVDC system are studied , and the transient characteristics of DC line fault voltage current under different pre - fault modes of operation are compared .
This paper analyzes the impedance characteristic of DC filter and its effect on transient process after fault , and puts forward that the DC filter can be regarded as fixed impedance in low frequency band characteristic analysis of transient voltage current signal of DC transmission line .
The effect of fault type , fault location and transitional resistance value on transient characteristics of DC line fault voltage is analyzed .
The lightning discharge calculation model of DC transmission line is studied , and the simulation modeling method of lightning current source , pole tower model , insulator flashover model and transmission line model in lightning transient simulation is given . Transient characteristics of DC line voltage current under fault lightning stroke and lightning stroke are analyzed .
This paper studies the formation mechanism of commutation failure of HVDC transmission system , judges the standard and the simulation method of single bipolar commutation failure , analyzes the transient characteristics of DC line voltage current in the case of commutation failure . The above work can provide a direct and effective reference for the transient analysis of the subsequent high voltage DC transmission system , and lays a foundation for the research of protection and fault location principle of DC transmission line .

( 2 ) To study the protection principle of HVDC transmission line considering fault selection .

The transient amplitude characteristic of the voltage mutation of DC transmission line after fault is analyzed . It is found that the magnitude of the voltage change of the fault pole line is greater than the perfect pole , and the integral value of the voltage mutation quantity can better reflect this feature ;
In this paper , the fault selection criterion of the ratio structure of the two - pole line voltage mutational quantity integral value is proposed , and the criterion threshold value setting method is given .
The transient polarity characteristics of the current abrupt change of DC transmission line after fault are analyzed , and it is found that the polarity of the current mutation at the two ends of the fault line is the same as that of the fault in the region , and the fault is the same in the area outside the fault line .
In this paper , a fault criterion is proposed in the region using the polarity of the current abrupt change in the fault pole line , and the polarity of the current mutation is extracted by the stationary wavelet transform . The main protection of the high voltage direct current transmission line is satisfied with the requirement of selectivity and quick action , and the criterion threshold value setting method is simple and independent of the simulation calculation ;
can be realized in the sampling frequency range of 10 kHz and above ;
only the polarity information of the terminal current mutation quantity is needed , the reliability requirement of the communication channel is low , and the method is particularly suitable for the case of needing to select a fault pole .

The PSCAD simulation model of 卤 660kV HVDC transmission system is established based on the actual parameters of the HVDC transmission project of Yindong 卤 660kV in China . The simulation data is used to verify the operating characteristics of HVDC transmission line protection principle under different fault conditions .

( 3 ) Research on protection principle of HVDC transmission line based on voltage and current abrupt change direction .

In this paper , the principle of direct current transmission line protection for direct current transmission line protection in DC transmission line is presented . The transient characteristic analysis of DC line voltage and current mutation rate after fault has been found , and the direction of voltage and current mutation of DC transmission line is different in the fault and out - of - area fault of DC transmission line protection zone .
The direction criterion of voltage and current mutation is proposed by comparing the integration value of voltage and current abrupt change over a period of time with the set threshold value .
In this paper , the protection principle of HVDC transmission line based on voltage and current abrupt change direction is proposed by comparing the voltage of two ends of the line and the direction of current abrupt change , and the criterion threshold value of the protection principle is not dependent on the simulation calculation ;
the fault in the DC transmission line protection area can be accurately recognized by using the directional information of the voltage and the current mutation amount of the two ends of the line , and the reliability requirement of the communication channel is not high ;
sampling data synchronization processing is not required ;
The voltage and current abrupt change direction criterion only calculates the integral value in the 5 ms data window , and can meet the protection criterion calculation requirement when the data calculation speed and the sampling frequency requirement are low , and the sampling frequency is 10kHz and above .

The operation characteristics of the protection principle in different fault conditions are verified by PSCAD simulation data of 卤 660kV HVDC transmission system .

( 4 ) The new algorithm of double - end travelling wave fault location of HVDC transmission line .

The propagation characteristics of fault traveling wave in DC transmission line are analyzed . It is found that the propagation process of fault traveling wave on the line can be characterized by the characteristic curve of the traveling wave head propagation characteristic . The fault location accuracy is not affected by the transition resistance value and the DC line outlet fault . The fault location error is about 0.1129 % of the total length of the line . The fault location error is basically the same as that of the existing high voltage direct current transmission project .

The research contents and achievements have important academic value for improving the theoretical level of DC transmission line protection and fault ranging theory , which can provide theoretical support for the construction of fast and reliable DC protection system , speed up the recovery speed of DC system fault and independent R & D of protection equipment .

【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM75

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