【作者】 任艳霞；

【导师】 刘明光；

【作者基本信息】 北京交通大学 ， 电力系统自动化， 2008， 硕士

【摘要】 由于电缆不受自然条件影响,体积小,不占线路走廊空间,安全可靠等多种优势,随着电网的发展和扩大,电缆在供电中发挥着越来越大的作用。但是,电缆一旦发生故障,查找困难,延迟恢复供电,为了保证电缆运行安全和快速诊断、修复故障,对电缆进行在线故障诊断与监测具有重要的工程意义。电力电缆离线故障测距技术已经基本成熟,但是电力电缆在线故障测距技术还不成熟。本课题通过对电力电缆故障测距的常用方法及新的故障测距技术进行系统分析和比较,要实现电力电缆的在线故障测距,需要考虑以下几个问题:中性点不接地系统是否能产生有效的故障暂态行波;故障信息在传播过程中的特性;故障点的特性对故障行波的影响;故障信息在测量点的变化特性;如何准确确定故障行波到达时刻等。本文以35kV交联聚乙烯绝缘电力电缆为研究对象,用PSCAD/EMTDC建立了一个电缆系统模型。用该模型仿真了不同中性点接地方式下的故障电流波形特征;仿真分析了故障点的特性对故障行波的影响;对电流行波进行了频谱分析。同时,采用小波变换局部模极大值的方法检测故障行波的突变点特征来判断是否发生故障,如果有故障发生则采用行波测距算法计算出故障距离,并对一个简单的电缆线路进行在线故障测距计算,验证在线故障测距的可行性。为了进一步实现对电缆故障的在线诊断,本文完成了电力电缆故障在线监测系统的软硬件设计。硬件部分主要包括信号调理电路设计,DSP工作电路设计、A/D转换电路设计、电源模块电路设计、存储器模块电路设计、逻辑模块电路设计。软件部分以Bd小波作为故障行波时刻检测算法。对于电缆端头不在变电站这种情况,安装在电缆端头的监测装置测试的数据就很难及时传输到变电站。为此,本文采用GPRS最新技术,开发了与GPRS配套的接口电路,还设计了专门的计算机操作软件与界面,通过GPRS技术进行数据实时传输,从而将非变电站内的电缆故障检测数据信息快速的传输回变电站调度中心,加速了对电缆运行管理和对电缆故障的快速处理。在实验室对监测与传输系统进行了模拟试验与联机调试,证明本系统具有一定的精度,能够正确工作,应用DSP为核心的监测装置和GPRS对电缆故障进行快速诊断具有可行性。更多还原

【Abstract】 Since the power cable having many advantages such as smaller volume, much more safety, it is extensively used in power supply system. But once fault occurs in the power cable, it is difficult to determine the fault location, and may disable the power supply. So it is of great significance to make on-line fault diagnosis and monitoring on the power cable. Off-line fault location for power cable and on-line fault location for overhead transmission line have been accomplished in the past several decades. In this paper, normal fault location methods and new technologies are analyzed and compared systematically. Several important and difficult problems should be thought of carefully. Firstly, whether or not can effective traveling wave due to cable fault be found to locate the fault point in cable system whose transformer neutral point non-grounded? Secondly, what’s the characteristic of the traveling wave during its propagation? Thirdly, will the fault point characteristic affect the traveling wave? Fourthly, how will the traveling wave change at the measuring point? And the last but not the least, how to determine accurately the arrival time of the traveling wave?This paper created a sample power cable system model with a transient simulation tool PSCAD/EMTDC based on a 35kV XLPE power cable. Within this model, the characteristic of fault current is simulated in different grounding modes, and so to answer the question whether or not effective traveling wave can be found in cable system whose transformer neutral point non-grounded. The characteristic of fault point is simulated to determine its effect to traveling wave. Besides, a spectral analysis is made to the fault current traveling wave. Using wavelet transform and local module maximum method to find break point is adopted, and judged the question whether or not the fault is happened by the criterion of fault traveling wave singularity. If that’s ture, the fault distance is worked out with the traveling wave arithmetic of fault location. As a case, on-line fault location is made to a sample power cable using wavelets, and thus to validate the feasibility of on-line fault location.For the usability of further testing the thesis and studying, design hardware and software of a on-line monitoring system of power cable fault location. The hardware of the system mainly including DSP(Digital Signal Processing) minimal system design, A/D conversion circuit design, power supply module design, the memory modulecircuitis designed, and the logical control module circuitis designed, and data transmission based on GPRS network. Data processing systems sotf mainly includinganalgorithm to pick-up the arrival time of the traveling wave based on Bd wavelet. Wemake simulation experiment and on-line debug in laboratory for this system, it provesthat the system satisfies the need of engineering measurement.更多还原