Research On Partial Discharge Causing Analysis And Detecting System For High-voltage Cables Of Electric Multiple Unit

With the development of high-speed railway in our country, the high speed EMUs havegot further development. So relevant technical requirements have also become much higher.And the mounting location of EMUs’ high-voltage cables are special. The reliability andsafety of high-voltage cables’ power supply is of vital significance for the operation of vehicle.As a result, the insulation test technology of high-voltage cables in EMUs has attractedconsiderable attention. But currently, to a certain extent, the insulation test of high-voltagecables in EMUs is mostly AC withstanding voltage test, while the partial discharge test ismuch less at home and abroad. And for the reason of interference, the result of test isunsatisfactory. Partial discharge test of EMUs’ high-voltage cables involves the technology ofhigh-voltage insulation and high-voltage test and so on. Through detecting the insulating stateof the cables, it judges hidden trouble and fault. In order to reduce the risk of power supplysystem, we must take necessary measures to deal with it.In this thesis, the readers will have a preliminary understanding after reading theintroduction of the basic structure of EMU high-voltage cables’ assembly and mountinglocation. Then classify and summarize the test methods of cable and circumstances andreasons of cable’s fault, and models of partial discharge of cable have been designedcorrespondingly. To aim at the system of partial discharge of EMUs’ high-voltage cables:firstly, we have designed a high-voltage power supply, which consists of hypogynousmachine composed of multifunction enhanced control panel LJD-51-XA+and epigynousmachine composed of the integrated machine built-in operating platform Windows CE5.0. Tomeet the function of voltage fluctuation and maintain the voltage in the process of partialdischarge test, the power supply make it by the communication of epigynous machine andhypogynous machine. Secondly, Testing system gets the pulse signal generated by partialdischarge by means of the LCR test impedance. And the author have processed the signal bymeans of the preamplifier circuit and anti-aliasing filter circuit. The discharge signal iscollected by waveform acquisition card (MP424) and transported to the industrial notebookcomputer built-in Windows XP operating system. To the software part, we adopt VB.NET asprogramming language. Thirdly, the author have realized the output and display of theamount of partial discharge and the interrelated parameters and frequency analysis etc afterprocessing the signal. Finally, because of the existence of interference during the test, theauthor have taken advantage of Wavelet Analysis to denoise and obtained ideal resultsthrough simulation verification. After grasping the reality of partial discharge of the cables,we can judge the insulation quality of EMUs’ high-voltage cables. And then we can take relative measures to handle the detected problems, and ensure the safety and reliability ofEMUs those are put into operation.