基于小波变换的直流系统接地故障检测

直流系统接地故障检测中常用的低频信号注入法容易受到各支路电缆中存在的对地电容的影响,在其基础上提出了基于小波变换的检测方法,该方法通过选取适当的小波函数,可以有效地克服对地电容的影响。当直流接地故障发生后,向直流系统中注入低频信号,利用小波变换算法从检测到低频电流中提取出与注入信号同频的低频电流,通过计算该电流信号中的阻性分量求得该支路的接地电阻值,从而可以判断出故障支路。经过m atlab仿真分析,这种方法可在对地大电容情况下都准确提取出低频电流相量特征,正确判断出故障支路。

Grounding Fault Detection of DC System Based on Wavelet Transform

The method of low frequency signal injection,which is usually used to detect grounding fault of DC system,is easily influenced by the capacitors between ground and each branch.In this basis,the method based on wavelet transform is proposed.By selecting the suitable complex wavelet function,the influence of direct earth capacitance can be eliminated efficiently.When the DC grounding fault occurs,the sine voltage signal with low frequency is injected into DC system.The complex wavelet transform algorithm extracts the sine current signal that has the same frequency with the injected signal from each branch current.Then the value of the resistance current that is included in the extracted current can be calculated to get the value of insulating resistance of each branch.At last,the fault branch will be found.The simulation results by Matlab proved that it can get the phasor characteristics of the low frequency current exactly in the case of high earth capacity and the fault branch will be found accurately.