Research On Fault Line Selection Method And Implementation Of Equipment In Distribution Network

With the continuous improvement of China’s power system,the distribution network is gradually developing in the direction of intelligence,and it is necessary to provide users with more reliable power supply quality.Single-phase ground fault is the most common type of fault in the distribution network.Failure to deal with the fault in time may cause fire in the cable channel in the city and increase the risk of large-scale blackouts,or even endanger personal safety,so it needs to be accurately and quickly identified Cut off the faulty line to reduce the impact on the user’s normal power supply.The engineering application of the existing fault line selection device on the market is not ideal.Currently,it is impossible to quickly select and remove the fault line.There are still some areas that use manual wire drawing method to select the fault line.Therefore,the single-phase ground fault line selection of the distribution network The development of methods and devices still has research significance and value.This paper first describes the research background and significance of the singlephase grounding fault line selection and device development of the distribution network,introduces the characteristics and applicable scenarios of the three neutral point grounding methods in the distribution network,and studies the occurrence of small current grounding systems.The steady-state characteristics and transient characteristics of single-phase ground faults summarize the existing fault line selection methods,and the selection injection method is the core algorithm of the fault line selection device.Then,starting from the principle of injection method,it analyzes how to select injection reasonably The size and frequency of the signal,and for the problem that the neutral point is incorrectly selected by the injection method in the grounding system of the arc suppression coil in the case of high resistance,this paper proposes a high frequency current signal injected from the neutral point of 180 Hz,and The phase difference of the injected current signal on each line of the distribution network is an improved injection method for the line selection criterion.Then build a 10 k V simulation distribution network simulation model on the MATLAB / SIMULINK simulation platform,simulate the typical characteristics of single-phase ground fault and build a neutral point simulation model based on the different frequency injection method,which verifies the theoretical feasibility of the method.This paper designs a single-phase ground fault line selection device based on the injection method for the dual-CPU power distribution network.The whole device adopts a rear plug-in structure.The main control CPU board,sampling board,power board,and in and out boards are all inserted on the general backplane.,The front panel of the device is equipped with Diwen DGUS LCD screen,the control unit of the main control CPU plug-in of the line selection device uses the STM32F407VGT6 chip,the control unit of the sampling board uses the STM32F427VIT6 chip,and the data acquisition unit uses the AD7606 chip.Control CPU control program,sampling board data acquisition program,LCD display and other programs,and built a 1200 V lowvoltage analog distribution network line model in the laboratory,and tested the singlephase ground fault line selection device developed in this paper.As well as the test of line selection accuracy,it fully verifies the feasibility and practicability of the singlephase grounding fault line selection device based on the different frequency injection method designed in this paper.