Fault Section Location And Identification Of Arc Grounding Fault In Coalmine Distribution Network

The working environment of coal mine is harsh.The cable is mainly laid in the high temperature and humidity underground roadway or mine working face.It often faces the scene of extrusion,flooding,chemical pollution,overvoltage and overcurrent,which leads to the accelerated damage of insulation,the intermittent arc discharge and the permanent grounding fault.Therefore,serious safety accidents are common.Accurate and fast fault identification and section positioning is of great significance to the line patrol staff.It can not only help them to easily and quickly troubleshoot faults,but also reduce the workload of line patrol and improve the efficiency of work.At the same time,it can also improve the power supply reliability of the coal mine power system,effectively guarantee the safe operation of coal mine power supply,and reduce the loss caused by power grid faults.It is conducive to the construction and development of smart grid in coal mines.In this paper,first of all,considering factors such as mine cable structure,grounding method and zero-sequence current acquisition.From two perspectives of steady state and transient state,the neutral point ungrounded mode and resonant grounding mode commonly adopted in mining power grids are used to discuss and analyze the current distribution characteristics under phase-to-earth fault.Then,based on the structure of three-core cable and relevant arc theory,the simulation models of continuous arc,intermittent arc and fixed resistance grounding fault are established in PSCAD.According to the simulation results,the influence of attenuated DC component contained in fault transient in resonant grounding system on arc process is discussed.Based on the established arc fault model,the transient process and time domain characteristics of each types of fault are studied,and the difference between attenuated DC component and transient capacitive component in fault current signal of non-effective grounding system is obtained under different fault angles.The influence of overcurrent disturbance on zero-sequence current in coalmine distributed network is discussed by building simulation model,and the starting threshold of section location method is set according to the amplitude of zero-sequence current.In terms of fault section location,by analyzing the current generation mechanism of grounding wire and combining with the variation law of transient attenuated DC component,a method of detecting the characteristic section of ground wire attenuation DC component is put forward.Considering the situation that DC component may not exist,taking the polarity of transient capacitive current as a supplementary criterion,a method of localizing the two characteristics is proposed.The two features complement each other and can be uploaded to the main station for discrimination after the operation of the local monitoring points.The requirements for synchronization and communication of the protection device are low,which is more suitable for the actual situation of the mine power grid.The simulation results show that the proposed method has a wide range of applications.Finally,the dispersion entropy feature of fault signal is extracted by wavelet transform,and the accurate identification and classification of fault is realized based on the method of machine learning.