Research On The Grounding Online Monitoring Device Of The Power Distribution System Of The EMU

At present,domestic EMUs are developing rapidly.Compared with Japan and Germany,although the domestic EMU development is relatively late,the total mileage of EMUs has come later.The safety of the EMU is very important for the development of the national economy,so the fault detection of each part of the EMU is very important.The EMU power distribution system is responsible for supplying on-board AC and DC equipment,and its reliability directly affects the driving safety of the EMU.One of the main faults of the current EMU power distribution system is the IT system ground fault.This paper analyzes and researches how to detect the ground fault of the power distribution system.First,the EMU distribution system is studied by constructing an IT system ground fault detection model,and then a circuit for detecting the system’s zero-sequence voltage is designed,and the formula for calculating the magnitude and phase of the zero-sequence voltage is derived,and the MATLAB/SIMULINK environment Build a simulation experiment model,compare the formula and the results of the simulation experiment,and prove the accuracy of the formula.On the basis of theoretical analysis,this paper builds an experimental platform,focusing on testing the single-phase and two-phase ground fault conditions.Finally,an online monitoring device was developed and developed.The device includes hardware,software and a host computer.The real-time measured data is transmitted through the host computer and installed and debugged on site.As a result,it can be successfully judged whether there is a fault and the fault phase is determined.This study uses fewer components,does not cause harmonic pollution to the distribution system,is economical and reliable,and provides a reliable theoretical basis for the ground detection of the three-phase three-wire distribution system of the EMU.Analysis of the test results shows that the experimental platform and the simulation model are basically the same.The test results show that the amplitude of the zero-sequence voltage will continue to decrease with the increase of RC,and the rate of decline also shows the same characteristics,and C_A,C_B,C_C have an effect on the size and reduction speed of the zero-sequence voltage.When the resistance of C to ground is equal,the amplitude of the zero-sequence voltage decreases with the increase of the three-phase-to-ground capacitance.Comparing the zero-sequence voltage phase with the phase A voltage phase can determine the ground short-circuit fault phase.Therefore,when a fault occurs,the degree of grounding can be judged by the amplitude of the zero sequence voltage first.If the fault is serious,you can continue to determine which phase line the fault occurred on.