中性点非直接接地系统零序网络的相频特性

Phase-frequency characteristics of zero sequence network in neutral indirectly grounding power system

暂态零序分量是中性点非直接接地系统单相接地故障选线的主要研究对象。为了揭示暂态量分布的频域特性,以线路分布参数模型为基础,全面分析了发生单相接地故障后的零序网络相频特性。通过PSCAD仿真分析了单条线路的零序阻抗相频特性曲线,研究了不同的线路参数、出线长度、线路结构和分支线路等因素对其的影响;仿真分析了整个零序网络中各条出线的相频特性曲线,研究了接地方式对其相频特性的影响。分析表明:单相接地故障发生后,故障线路测量到的是所有健全线路组成的零序网络的相频特性,其特性取决于系统接地方式以及健全线路的相频特性;线路首容性频带并不是一成不变的,基于暂态零序信号的选线方法要能够自适应地寻找线路的首容性频带,提取频带内的暂态信息。并且要依据频带内各条线路电流之间或电压与电流之间的关系形成选线判据。

Transient zero sequence current is the focus of faulty line selection in neutral indirectly grounding system. In order to study the frequency-domain characteristics of transient signal distribution,the phase-frequency characteristics of zero sequence network with single-phase grounding fault is analyzed based on the distributed parameter line model. The phase-frequency characteristics of single feeder zero sequence impedance are analyzed by PSCAD simulation and its influencing factors are studied,such as transmission line parameter, length, structure, branch, etc. The phase-frequency characteristics of zero sequence network are also analyzed by PSCAD simulation and the influence of grounding mode on it is studied. Analysis shows that,what is measured on the faulty line is actually the phase-frequency characteristics of zero-sequence network composed of all healthy lines,depending on the characteristics of all healthy lines. The first capacitive adaptively found by the faulty line selection method based neutral grounding mode and the phase-frequency band of lines is on transient zero changeable,which should be sequence current to extract the transient information and set selection criteria according to the relationship between zero sequence current and voltage or between zero sequence currents.