Research On Single-phase Grounding Fault Line Selection Method Of Distribution Network Based On Traveling Wave Panoramic Waveform

After the single-phase ground fault occurs in the small current grounding system of distribution network,Whether the ground fault line can be selected quickly and accurately is not only related to the safe operation of the power system,but also an urgent problem to be solved to realize the intelligentization of the power distribution system in my country.Single phase grounding fault is easy to occur in small current grounding system.If it is not removed in time,it is easy to develop into multi-phase fault and expand the scope of the accident.Therefore,it is of great practical significance for the safe and reliable operation of power system to select the fault line accurately and deal with the fault in time.The thesis first analyzes the generation and transmission mechanism of fault traveling waves.On this basis,Combining the structural characteristics of the distribution network itself with numerous branch nodes,cable hybrid connection,and ground capacitance of the busbar system,the transmission and transformation characteristics of broadband traveling wave are mined,and the essence of fault traveling wave signal changing according to frequency is revealed.Thus,the time-frequency domain traveling wave panoramic waveform containing the change characteristics of amplitude-polarity-frequency is derived.Aiming at the problem of weak anti noise ability of signal time-frequency analysis method,a time-frequency analysis method based on synchronous compression wavelet transform is proposed.By squeezing the time-frequency information of continuous wavelet transform in frequency domain,this method can effectively improve the aggregation of time-frequency distribution energy and reduce the distortion of instantaneous frequency.In the face of strong noise interference,it still shows good time-frequency analysis characteristics.In order to effectively improve the accuracy and reliability of single-phase grounding fault line selection in the distribution network,a method of fault line selection in distribution network based on traveling wave panoramic waveform is proposed.This method integrates the amplitude-polarity-frequency multi-dimensional characteristic information of panoramic waveform.Then,based on the principle of waveform similarity,the traveling wave panoramic waveform of faulty line and healthy lines are analyzed quantitatively,and a similarity degree coefficient matrix is constructed for each line.By calculating the comprehensive correlation coefficients of each line,the difference between the traveling wave panorama waveform of the faulty line and the healthy line can be magnified.There is no need to extract the initial wave head of the traveling wave,and no need to manually set the threshold,which realizes the fast and accurate fault line selection of the distribution network.The simulation results show that the time-frequency analysis of the proposed synchronous compressed wavelet transform is compared with that of the continuous wavelet transform.In the environment with strong noise,the synchronous compressed wavelet transform can get a time-frequency curve with higher accuracy,which verifies that the algorithm has good robustness to noise.The fault line selection method of distribution network based on traveling wave panoramic waveform is proposed in this thesis.When single-phase grounding faults occur under different working conditions,this method can still accurately capture fault characteristics to achieve rapid and accurate line selection,and has strong adaptability.