| As a power supply terminal,the low-voltage distribution network has the outstanding characteristics of many branch lines,complex topology,and strong concealment of line laying.While the low-voltage distribution line completes its power supply task,the electrical safety problem is becoming more and more prominent.Among them,electrical fire has become a prominent problem in electrical safety because of its characteristics of great harm and wide influence.According to official statistics,in the past ten years,the proportion of electric fire has accounted for more than 30% of the total number of fires every year.Among all kinds of electric fire causes,arc failure caused by aging lines,insulation damage and poor contact has become an important cause of electric fire.Among them,series arc fault is difficult to detect because of its weak fault characteristics and easy to be confused with nonlinear load.In addition,the realization of online fault location in the complex line topology eliminates electrical safety hazards and reduces the investment in manual inspection,which is also an important issue related to the power supply reliability and safe consumption of low-voltage distribution system.Aiming at the problems existing in current arc fault research,this paper mainly carries out the following research contents:(1)Taking multilevel distribution lines as the research object,the distribution lines are set as fault-free,first-level arc fault,and second-level arc fault according to the existence of arc and the location of arc faults,and the voltage and current distribution of each node in the three scenarios are analyzed one by one.By integrating the voltage and current information of each scene,electrical signals are selected in the study of arc fault detection and location in the multilevel circuit scene.(2)According to GB 14287.4-2014 arc testing requirements,the arc fault experiment platform was designed to collect typical load arc experimental data considering load types.By analyzing waveform characteristics of typical load terminal voltage(downstream voltage of fault point),the voltage signal harmonic energy distribution information in the whole frequency band was selected as fault characteristics.At the same time,it is found from the measured data that due to the randomness of arc combustion,arc starting resistance varies in the range of 0.5～100kΩ.Therefore,a segmentation arc model is established with arc starting resistance as the main parameter to complete the analysis of the influence of arc starting resistance on voltage fault characteristics.(3)According to the fault characteristics of the signal to be analyzed and combined with wavelet energy spectrum entropy,a series arc fault detection method based on the voltage characteristics of the load terminal is proposed.At the same time,taking fault feature multiple and entropy fluctuation variance as core parameters,the optimal algorithm parameters were selected from 16 wavelet bases such as Haar,Db,Sym and 1～6 decomposition layers to complete algorithm optimization.The effectiveness of the proposed method is verified from the perspectives of load type,arc resistance size,load switching effect and correlation algorithm comparison.(4)The fault characteristic distribution of voltage at all levels of nodes in distribution lines is studied under the influence of line impedance.Based on the analysis of the characteristic law of multilevel distribution line node voltage,combined with the traditional matrix location algorithm and case-based reasoning decision method,a series arc fault location method applied to low-voltage distribution system was proposed.By adding fault information weight factor,the accuracy of the algorithm was improved.Through model simulation and simulation experiment,the voltage distribution characteristics of multilevel lines are verified,and the positioning fault tolerance under the condition of false detection and missing arc fault is verified by comparing algorithms. |
PDF Full Text Request