注入变频信号检测电网对地电容的改进  

Improved Injecting Variable-frequency Signal Method for Detection of Distribution Network Line-to-earth Capacitance

作　　者：程路[1] 陈乔夫[1] 谢冰若[1] 张宇[1] 

机构地区：[1]华中科技大学电气与电子工程学院,武汉430074

出　　处：《高电压技术》2009年第4期943-948,共6页High Voltage Engineering

基　　金：国家自然科学基金(50477047)~~

摘　　要：准确检测电网对地电容是谐振接地系统有效补偿的基础注入变频信号而检测法具有不需要启动电感调节装置,不改变系统运行状态,二次回路测量等诸多优点,但中性点位移电压的存在会影响注入信号的质量,同时给注入信号的相位判断带来困难。为此基于变压器可控负载原理的消弧线圈提出了运用电压前馈校正改善信号源输出电流特性,检测中性点注入信号电压幅值判断谐振点的改进措施。系统动模实验表明,对于中性点最大位移电压达900V的电网,改进后的方法仍具备很高的电容检测精度,验证了所提方法的有效性。该方法经适当调整也适用于其他类型消弧线圈的自动调谐。Accurate detection of distribution network line-to-earth capacitance is the fundamental of effective compensation in neutral resonant grounding system. Injecting variable-frequency signal method has many advantages such as not needing adjust inductance of arc-suppression coil, unchanging running status of power system, secondary circuit measurement, etc. However, the existence of neutral point displacement voltage could affect the injected signal, which may make the phase judgement inaccurate. We analyzed these problems on the basis of the transformer with load controllable arc-suppression coil, and achieved two improvements for signal injection method, that is： adopting voltage feed forward control to improve the characteristic of the injected signal and detecting the magnitude of neutral point signal-frequency voltage to judge the resonant state. The experimental results demonstrate that ,even for high neutral displacement voltage up to 900 V in power network, the improved method still has excellent detecting precision, verifying the validity of the proposed methods. These improvements are applicable for automatic tuning of other type of arc-suppression coil by proper adjustment.

关 键 词：变频信号法 对地电容检测 消弧线圈 前馈控制 幅值比较 动模实验 

分 类 号：TM86[电气工程—高电压与绝缘技术]