李景丽,袁豪,徐铭铭,田凤兰.小电阻接地系统高阻接地故障检测技术综述[J].电测与仪表,2023,60(6):10-18. Li Jingli,Yuan Hao,Xu Mingming,Tian Fenglan.Overview of High Impedance Fault Detection Technology in Small Resistance Grounding System[J].Electrical Measurement & Instrumentation,2023,60(6):10-18.
小电阻接地系统高阻接地故障检测技术综述
Overview of High Impedance Fault Detection Technology in Small Resistance Grounding System
When high impedance fault occurs in a small resistance grounding system, the current is less than the traditional zero-sequence current protection action threshold, and arcs are often accompanied.It is difficult to accurately detect and remove high impedance faults. In this paper, firstly, the characteristics of bus zero sequence voltage and each outlet zero sequence current in single-phase high impedance fault of small resistance grounding system are analyzed theoretically; Then, for the arc phenomenon that often accompanies high impedance faults, starting from the physical process of fault ignition arc, the physical approximation process, numerical derivation process, experimental verification and applicable conditions of six arc models, such as the commonly used Cassie arc model, Mayr arc model, improved Mayr arc model, Mayr-Cassie combined arc model and Emanuel circuit model, are analyzed in detail. Finally, the signal processing process, fault feature extraction, advantages and disadvantages of detection methods in the high impedance grounding fault detection method are analyzed,from the volt-ampere characteristic analysis method and the zero-sequence current distortion method in the time domain and the fault current signal method and the fault voltage signal method in the frequency domain. And it is considered that it has clear mathematical and physical significance to use the waveform slope curve change which is caused by the zero-sequence current waveform’s distortion near the zero-crossing point as the fault feature. The energy ratio of high frequency band and low frequency band of zero-sequence voltage signal that is decomposed by the wavelet packet and is used as the fault feature, which is not affected by the fault conditions, system structure and other factors, and has a good detection effect.