基于信号注入法的铁磁谐振与单相接地故障辨识

中性点不接地系统中,电磁式电压互感器(PT)铁磁谐振与单相接地均频繁发生,其故障现象相似,都表现为零序电压升高,特别是基频谐振不易与单相接地区分,导致微机消谐装置与小电流接地选线装置可能发生误判。本文通过分析基频谐振与单相接地的线路对地阻抗的差异,提出基于信号注入的故障辨识方法。该方法依据不同故障类型下,同一注入电流信号产生电压的不同来辨识基频谐振与单相接地故障。仿真结果验证该方法能够有效辨识基频谐振与单相接地故障。

Distinguish Ferroresonance from Single-phase Earth Fault Based on the Approach of Signal Injection

In an isolated neutral point power system,potential transformer ferroresonance and single-phase earth fault are very frequent,and the phenomenon of them is similar,the zero-sequence voltage showing high for a long time.Because of the problem of distinguishing fundamental frequency ferroresonance from single-phase earth fault,the PT-resonance-eliminator and the fault-feeder detector could not tell the difference between two fault types well,they are apt to make the wrong judgments in some cases.The approach of signal injection is put forward by analyzing the difference of line-to-ground impedance between fundamental frequency ferroresonance and single-phase earth fault.As the injection current is fixed,it will produces different voltage to different fault types.This method is used to identify fundamental frequency ferroresonance from single-phase earth fault based on the above.Verification by simulation data reveals that the approach is right and effective.