A fault line selection method for resonant earthed system with high accuracy
SONG Jinzhao;LI Yongli;SHI Zheng;MA Lifan;College of Electrical and Automation Engineering, Tianjin University;
To solve the problem of low accuracy of fault line selection in resonant earthed system when the fault switching angle is small, a novel fault line selection method is proposed by taking the advantage of Ensemble Empirical Mode Decomposition(EEMD) and Hilbert-transform in frequency band analysis. By analyzing the distribution characteristics of transient zero sequence current and comparing the energy of transient capacitance current with that of decaying DC component, the signal with higher energy is used for fault line selection adaptively. When the energy of transient capacitance current is higher, the fault line is identified by comparing the polarity of transient capacitance current. When the energy of decaying DC component is higher, the fault line is identified by comparing the decaying DC component energy of arc suppression coil with that of primary selection line. Simulations of single-phase earth fault under different switching angle and transition resistance conditions have been done, the results show that the proposed method has high accuracy and can select the fault line even in small fault switching angle occasions. The proposed method may take effect in its applications.