Methods Research On The Detection Of The Single-phase-to-ground Fault In The Distribution Network

At present,China's medium-voltage distribution network basic non-effectively grounded neutral point operation mode,single-phase fault-prone and makes the safe and reliable operation of the distribution network received threats on distribution feeder,distribution network in fault conditions Under the long run will lead to the distribution network insulation damage,or even cause a fire and make Ben distribution network collapse.Therefore,how to quickly detect distribution network fault occurs or not,and accurately identify the fault lies in the distribution lines,for the safe and reliable operation of the distribution network and the power systems have a very important significance.This paper describes the status of research Faulty line at home and abroad,for deficiencies existing in the presence of a fault line selection method were analyzed and discussed,and in the following aspects of the distribution network of single-phase ground Fault detection methods are described.Firstly,the un-grounded power distribution mathematical model of single-phase ground fault through MATLAB/SIMULINK simulation established a neutral point un-grounded distribution network model of the distribution network in a single feeder phase to ground fault simulation to verify the fault feature un-grounded system of single-phase ground fault,that fault phase voltage drop after failure,sound phase voltage rises,the fault current is large,fault lines and perfect zero-sequence current flows to the contrary.Secondly,the neutral point arc suppression coil grounding phylogenetic distribution network mathematical model of single-phase ground fault is discussed,the article analyzes the single-phase ground fault occurs after the distribution network of transient and steady-state characteristic features,Starting from the perspective of the mathematical model describes the fault feature small current grounding system and verified by simulation modeling features of these failures.Again,the article based on the spectral distribution of the small current grounding system of single-phase ground fault circuit zero sequence current distribution network,the analysis found that the fault line and healthy line of zero-sequence current fault features are distributed in different frequency bands,paper selected wavelet The method of zero-sequence current of each of the wavelet decomposition of the malfunction,the wavelet coefficients of the largest and second largest energy principles to select the two groups corresponding to the characteristic frequency band,and then use the correlation analysis method comparative correlation between these two groups of wavelet coefficients By setting the line selection process first elected reliable fault line,which takes full advantage of the small current grounding system fault feature single-phase ground fault occurs,the line selection algorithm principle is clear,simple steps to achieve reliability.Finally,by analyzing the equivalent model of small current grounding system single-phase ground fault occurs,the analysis was sound feeders in each of the ground capacitance charging amount of charge to its zero-sequence voltage linearly related to the amount of charge while charging and fault lines zero-sequence voltage without significant linear correlation,based on this,correlation analysis method comparative fault occurs after the electric charge of each line-zero-sequence voltage image,get a new method of fault detection.