Research On Fault Line Selection Of Single-Phase Grounding In Small Current Grounding System Based On Wavelet Analysis

At present,low current grounding system is mainly used in medium and low voltage distribution network in China.The frequency of single-phase grounding fault in this system is higher,and the grounding current is smaller after the fault occurs,and there is no obvious fault feature,so it is difficult to detect it effectively.Many scholars have studied the single-phase-to-ground fault line selection in low current grounding system.Although some achievements have been made,there is no substantial solution to it,which has a certain impact on the improvement of the automation level of distribution network.This paper mainly studies this aspect,and applies the wavelet analysis method to the single-phase grounding fault line selection research of the small current grounding system.Firstly,the specific characteristics of single-phase grounding fault in small current grounding system are analyzed in detail,including various high-frequency information in the transient process after the fault occurs.Then the theory of wavelet is elaborated comprehensively,including the concrete principle,method and application process.Wavelet analysis can decompose the signal into several frequency bands,which is more suitable for the analysis of non-stationary and transient signals.Then,based on the wavelet theory,a method of fault line selection is constructed,which is based on the principle of wavelet transform modulus maximum singularity detection.This method has high applicability.It can identify fault lines according to the magnitude and polarity of wavelet modulus transform coefficients of transient zero sequence current in the frequency band of fault line selection,and the recognition results can achieve high accuracy.Secondly,using the simulation process of MATLAB/Simulink tool,the 35 kV bus-strip three-way model of neutral point grounding system via arc suppression coil and non-grounding system is simulated,and the fault characteristics of this grounding mode are simulated and calculated by the method proposed in this paper.The simulation results show that the detection of fault lines by wavelet analysis has high accuracy and efficiency.It can find the fault line in a short time and lay a foundation for the treatment of the line fault.Finally,the line selection device is designed in detail.Firstly,the basic characteristics and functional requirements of the line selection device are studied.Then,the single-phase grounding fault line selection device of distribution network is designed reasonably,including its overall structure design and functional module design.Figure [48] table [3] reference [63]...