Design And Implementation Of Online Monitoring And Management System For Cable Ground Fault In Ring Network Cabinet

With the rapid development of power industry,Ring network cabinet plays an increasingly important role in urban power construction.When the cable grounding fault occurs,it may cause power outage,which has a bad impact on the normal operation of the power system.It is necessary to locate the fault point in time accurately,carry out rapid troubleshooting and maintenance.At present,residual current increment method,first half wave method,fault indicator method and signal injection method are often used,but these methods have poor judgment effect on high transition resistance grounding fault,and the success rate of grounding fault identification is not high.Therefore,this paper studies the cable grounding fault online monitoring system based on zero sequence current difference method.The system can accurately judge the fault of the line and monitor the data in real time,which has important practical significance for the safe operation of the distribution network.A distribution network model based on regional parameters is established firstly,and then it is analyzed according to the regional parameter model of distribution network.By dividing the distribution network into several areas,the online monitoring system is used to measure the difference of zero sequence current,and the difference of zero sequence current is used to judge whether the line has grounding fault;at the same time,set up the ground fault The distribution network model of two grounding modes,which are direct grounding of neutral point and neutral point grounded by arc suppression coil,is established.And the Matlab/simulink simulation model is established.The paper proposes that the parameters of the distribution of the line to ground before and after the fault are solved by using bias capacitance to solve the single-phase and two-phase grounding conditions respectively.According to the change of the distribution parameters before and after the fault,the phase to ground is determined.The model is based on the change of the distribution parameters before and after the fault The method is not affected by the grounding mode,and can be used to judge the high resistance grounding accurately,which is very general.An online monitoring device for cable grounding fault of ring main unit is developed by using embedded technology.The on-line monitoring device includes the collector at the incoming end and the collector at the outgoing end.The collector at the incoming end uses the zero sequence current transformer to collect the zero sequence current at the incoming end,the three-phase voltage transformer to collect the three-phase voltage at the incoming end,and the collector at the outgoing end uses the zero sequence current transformer to collect the zero sequence current at the outgoing end By using Lora wireless communication technology,the zero sequence current collected by the outgoing line collector is sent to the incoming line collector to judge the grounding fault,in which the incoming line collector communicates with the server through 4G DTU to realize the efficient storage of data;Finally,combined with MySQL database,on the platform of visual studio 2017,the online monitoring and management system of cable grounding fault of ring main unit is developed by using C # language,which realizes data query,management and forms various reports.The online monitoring system for cable grounding fault of ring main unit meets the development requirements of the client through actual test,and can accurately judge the grounding fault,especially the judgment of high resistance grounding fault,which verifies the reliability and practicability of the system.The use of the system is of great significance to guarantee the power supply quality of the power system.