Design And Implementation Of Cable-fault Detector Based On Chaos Time-domain Reflectometry

With the improvement of equipment automation level, cable is the key power transmission equipments and the main carrier of information transmission, it is widely applied in the aircraft, high speed multiple units and spacecraft. Its laying mode and laying environment are complex increasingly, open circuit and short circuit fault occurred frequently. It is urgent to develop high precision and intelligent cable fault detector, the rapid and accuracy cable fault inspection can improve the reliability of power supply, reduce the reparation fee and avoid the unnecessary losses. Existing domestic cable detector has some disadvantages in the practical operation, such as low detection accuracy, not on-line detection and so on.To achieve more precise and on-line fault location, in this thesis, we propose the introduction of broadband chaotic signal to the cable fault detection. A cable-fault detector based on chaos time-domain reflectometry is presented. This thesis contributes to cable-fault detection in the following six aspects.1. First, we introduce the causes of the cable fault and fault type, and then the advantages and disadvantages of the existing cable fault detection methods was summed up, and propose the methods of chaotic time-domain reflectometry to the cable fault detection.2. The methods of generating the broadband microwave chaotic signal in the electric field and the advantages in cable fault detection is studied, the nonlinear dynamic characteristics of the Boolean chaotic circuit were studied by numerical experiment, including the route to chaos, the largest Lyapunov exponent, and peak noise ratio of correlation trace. The time domain, frequency domain and autocorrelation characteristics of the output signal in the periodic and chaotic states are analyzed.3. A prototype of cable fault detector based on chaotic time-domain reflectometry is developed, the hardware structure, software function of the system and core algorithm design are described in detail.4. To verify the performance of the cable fault detector, The experiments are carried out on the URM43 coaxial cable as the cable under test. the results show that the system can locate precisely short circuit, open circuit and impedance mismatch on coaxial cable. The relative error of measurement results is within 0.18% in the range of 200 m, the absolute error of the measurement is less than 36 cm. The maximum range is about 1 600 m and the relative error of measurement results is within 4.3%.5. More importantly, the cable-fault detector has better capability in on-line detection. Open and short circuits on cables in the live communication system can be located in the experiments, and the error rate of the communication system induced by the chaotic signal of the detector is within the order of E-09. In addition, an experimental device was set up to simulate the wet arc fault, and on-line detection of the wet arc fault was carried out. The measurement results show that the cable fault detector can effectively detect the wet arc fault of the cable in the power transmission system.6. A new improved system has been built based on chaos time-domain reflectometry by using signal acquisition card in this paper. Based on the LabVIEW platform, software program was secondary developed. By using the new system, main technical parameters are tested and compared with the prototype of cable fault detector.