Design Of Cable Fault Detector

This thesis designs a kind of Cable Fault Detector based on spread spectrum Time Domain Reflectometry(SSTDR)to detect and locate cable faults online.This thesis analyzes the types and causes of cable faults,studies the reflection and transmission of traveling wave signals when impedances of the cable do not match by establishing a cable distributed parameter model,demonstrates and analyzes the detection sequence of SSTDR method,analyzes the principle of location of the cable fault,expounds the algorithm of Cable fault location,and designs the overall architecture of cable fault detection system.According to the overall framework of the cable fault detection system,the hardware design of the cable fault detection system is carried out.The fault test signal generation module mainly uses FPGA to modulate DDS fault detection signals and controls DAC to output cable fault test analog signals.The signal acquisition and storage module mainly uses FPGA to control ADC to acquire cable fault reflection signals,and uses SDRAM as the external memory of FPGA to store the acquired data in SDRAM.The data operation module mainly uses DSP to process the data collected by FPGA,and then outputs fault test results and fault point distance.Direct Digital Frequency Synthesis(DDS),SDRAM dynamic random access memory control program,static random access memory SRAM control program,FPGA and ADC,DAC chip interface program and DSP-based related algorithm program are written.A prototype of Cable Fault Detector is made,and the feasibility of SSTDR method is verified through the experimental test of the faulty cable.The experimental results show that the designed Cable Fault Detector can accurately judge the cable fault type and calculate the cable fault distance more accurately.The Cable Fault Detector prototype meets the relevant design requirements.