中文摘要：

针对小电流接地系统单相接地故障的谐波选线原理,分析了电源侧、负荷侧和故障点自身的谐波源及其产生的故障谐波电流特征,在分别分析其独立作用对谐波选线影响的基础上,综合分析了多谐波源共同作用时对谐波选线的影响。研究表明：电源侧和负荷侧谐波源起主导作用,其主要通过故障点故障前谐波电压体现;故障点谐波源产生的谐波电流小、作用可忽略;各谐波源的大小、相位和故障点相对谐波源的位置是影响谐波选线的主要因素。仿真验证了上述观点。

英文摘要：

According to the principles of harmonic-based earth fault protection（identification to the line with a single phase to earth fault） in non-solidly earthed network,the characteristics of non-linear load,system power,fault point as a harmonic source and the faulty harmonic current generated by them are analyzed.Through harmonic-based protection system,the influences of multi-harmonic sources are studied as well.It is discovered that the harmonic sources of system power and non-linear load play dominant roles which give their effect through the pre-fault harmonic voltage at the fault point.The influences of fault point can be neglected for it produced neglected harmonic current.The magnitude and phase of harmonic sources and the distance between fault point and harmonic sources are the main factors affecting the reliability of harmonics-based protections.The analysis results are proved by digital simulation.