【摘要】 分析了低频信号注入法的原理及存在的缺陷,针对其缺陷提出了基于小波变换的直流系统接地故障检测方案。发生接地故障后,向直流系统正负母线注入低频正弦电压信号,利用各支路的电流互感器检测出支路中的低频电流信号,通过小波变换从中提取出与注入信号同频的正弦电流信号,计算某支路电流信号中的阻性分量即可求得该支路的接地电阻值,从而判断出故障支路。大量的数值仿真和实验研究验证了该方法的可行性。更多还原

【Abstract】 The principle and existing defects of low frequency signal injection method being used to detect the grounding faults in DC systems of power plants and substations are analyzed. According to these defects a wavelet transform based detection scheme for grounding faults in DC system is proposed. When grounding fault occurs, a low frequency sinusoidal voltage signal is injected into both the positive and negative buses of DC system and the corresponding low frequency current signals in all branches can be measured by use of the CTs in these branches, then through wavelet transform the sinusoidal current signals which are of the same frequency as that of the injected signal can be extracted from these current signals. Calculating the resistance components of the extracted current signals of a certain branch the grounding resistance of this branch can be obtained, thereby the faulty branch can be determined. A lot of simulation and test results show that the proposed scheme is feasible.更多还原