Study On Fault Line Selection Of Small Current Grounding System Based On Harmonic Wavelet Packet And Chaos

The stability of power supply system has become very important to people’s daily life, relating to the development of the world. The small current grounding system is in the process in our country at present, causing great inconvenience to the users. Interference and uncertainties of various factors makes the fault line selection more difficult. Therefore, the study of single-phase fault line selection of the small current grounding system has become a hot topic of current research.This article discusses the mechanism of single-phase ground fault of the neutral point arc suppression coil grounding system and the neutral point ungrounded system, determines the fault line selection basis, and laid the foundation for determining line selection scheme.Then the principle of harmonic wavelet packet method is introduced, theoretical analysis shows that this method can achieve fast and no signal aliasing separation, and through experiments to verify its advantage in signal analysis and its feasibility in power system fault diagnosis. Study the chaotic oscillators weak signal detection method, introduced time-scale transformation method to let it to adapt the detection needs of large experimental frequency signal. The harmonic wavelet packet method combined with chaotic oscillators gives the small current grounding system’s single-phase ground fault line selection scheme.Finally, a small current grounding system model by ATP-EMTP power system simulation software is built, and the obtained zero sequence current signal by MATLAB software are analyzed. The zero sequence current is processed by harmonic wavelet packet and the fifth harmonic component are extracted. The extracted sequence are introduced into the chaotic oscillator as an external driving force, the fault line could be selected accurately by observing the changes in the system’s phase diagram. Experiments to a variety of fault situation showed the effectiveness of the line selection scheme. The experimental results showed that this scheme could select the fault line correctly, and with high reliability.