一种配电网高阻接地故障在线监测与辨识方法

Online criterion and identification of single-phase ground fault with high resistence in distribution network

中性点不接地系统的配电网高阻接地故障是一种多发故障,短路电流小,故障特征不明显,在线辨识困难,导致故障初期难以被发现,极易演化成严重故障。通过研究其单相接地的暂态过程,发现故障暂态电容电流会使故障线路零序电压有明显的高次谐波,经10k V配电网单相高阻接地后故障线路零序电压频谱分析仿真结果证明了这一点,因此可将其作为高阻接地故障在线辨识的特征谐波。为了确定该故障特征谐波的有效性,分别与其他故障类型和配电网突加突减负载时的零序电压进行了仿真对比分析,从而证实了该谐波可以有效区分其他情况产生的谐波。为了进一步探索高阻接地故障参数对故障特征谐波影响的规律,分别对不同故障接地电阻和不同故障相角时的线路零序电压暂态过程进行了仿真,结果表明,故障发生于相电压90°相角时,该故障特征谐波幅值最高,约为基波幅值的4%～9%,且幅值随故障电阻升高有规律的减小。该特征谐波特征明显,足以用于准确在线辨识高阻接地故障,从而为配电网在线故障辨识设备的研究提供了新的思路。

The high-impedance grounding fault of a distribution network in neutral ungrounded system occurs frequently.When the fault occurs,short-circuit current value is small,which caused unobvious fault characteristic and difficulty online identification.So it will be hard to notice the fault in initial stage and easily falls into a serious fault.Through studying the transient process of single-phase grounding fault,it is founded that the transient capacitive current of the fault will caused significant higher harmonics in zero-sequence voltage waveform.The above viewpoint was proved by the spectral analysis of the zero-sequence voltage after the single-phase high-impedance grounding fault happening in 10 k V distribution network＇s simulation.Thus,the higher harmonics can be used as high-impedance grounding fault online identification characteristic harmonics.In order to ensure the uniqueness of the characteristic harmonics,the simulated contrastive analysis of the zero-sequence voltage was compared between other fault types and sudden add-subtract load condition.For further exploration to the law that how the parameters of the fault affects the characteristic harmonic,the fault is simulated at different phase angles and different fault resistances.The results show that when the fault occurred at 90 ° phase angle of phase voltage,the amplitude of characteristic harmonic is maximum,ranked about 4% ～ 9% of the fundamental amplitude.And the amplitude decreases regularly while the fault resistance increasing.With obvious feature,the characteristic harmonic is qualified for the accurate singlephase high-impedance grounding fault identification.Thereby,the method provides a new idea for the research of device for the power distribution network fault identification.