Research On Leakage Current Monitoring And Leakage Protection Technology Of Low Voltage Lines

For a long time,low-voltage distribution network personal electric shock accidents and electrical fire accidents occur from time to time,which seriously affect the safety and reliability of power supply.Leakage current protection is a system engineering,which mainly involves the coordination of residual current protection technology and a variety of low-voltage system grounding methods.At present,the residual current protection mainly relies on the residual current device(RCD)to achieve,with its effective role in preventing personal electric shock and electrical fire caused by single-phase grounding,it has been rapidly developed and popularized.However,in the traditional centralized control distribution network environment,RCD can not be applied in many occasions.For example,in TN-C-S grounding mode,there is a large normal leakage current in the line and load,and part of the neutral line current of the system returns from the earth,which will also lead to the increase of residual current at the distribution transformer,resulting in the RCD of the downstream main line on the power side can not be put into operation.Therefore,based on the residual current protection device,this paper mainly studies the leakage current fault monitoring and sectional location method for various grounding systems.The specific work of this paper is as follows:(1)By analyzing the residual current waveform difference characteristics of both sides of the fault point when leakage current fault occurs in low-voltage line section caused by singlephase grounding,Hausdorff distance algorithm is introduced.The distance value represents the difference degree of residual current between adjacent terminals.The fault section is determined by the unified fault criterion,and its recognition ability is not affected by the downstream normal residual current caused by various reasons It improves the sensitivity of monitoring and can be applied to various grounding modes.In order to complete the rapid detection of line leakage fault in substation area,it is necessary to realize the automatic identification of low-voltage network topology.Aiming at the problems of frequent changes and low accuracy of low-voltage distribution network topology,one of the key supporting technologies is proposed,which is the topology identification technology based on switch mutation component,This method has low cost and small amount of calculation,and is suitable for low-voltage distribution network.In addition,the synchronous acquisition of multi-point voltage and current phasors in low-voltage distribution network is the basis of leakage fault detection,instantaneous line loss and many other applications.To solve this problem,an accurate clock synchronization technology based on power carrier is proposed.This method uses the correlation analysis of disturbance signal and time characteristic signal to obtain the relative error between clocks,so as to adjust the sampling time and analyze the method reasonably It makes use of the characteristics of low-voltage distribution network,does not rely on communication channels,and does not need additional special timing devices,so it has the conditions for wide application in low-voltage distribution network.(2)In view of the characteristics of low-voltage distribution network,such as large quantity and wide range,complex network topology,various types of electrical equipment,lack of technical file management,large changes in network structure,and difficult to restore the topological relationship of power grid,the establishment of intelligent low-voltage distribution Internet of things management system is a prerequisite for the application of leakage current fault monitoring method and key supporting technology based on Hausdorff distance,which makes the low-voltage distribution network stable Realize informatization and realize automation and intelligence on this basis.(3)The leakage current fault monitoring method based on Hausdorff distance and the topology identification technology based on switch mutation component are simulated and analyzed by using the simulation software atp-draw and MATLAB.Through the analysis of the simulation data,the feasibility and correctness of the leakage current fault monitoring method and topology identification technology proposed in this paper are verified.