Analysis of Time-Domain Reflectometry Combined With Wavelet Transform for Fault Detection in Aircraft Shielded Cables

The detection of faults in aircraft wiring systems is always a significant research. Although several reflectometry methods have been proved to be effective technologies for locating open and short circuits on wires, they do not assess well the faults, such as abrasions and frays. This paper analyzes the feasibility of a combination of the time-domain reflectometry (TDR) and wavelet method for detecting the faults on aircraft lossy shielded coaxial cables. A mathematic model is presented for simulating the propagation of wave in the cable with the fault based on TDR. A step wave generator with a steep rising edge is constructed and implemented to detect the faults. The wavelet method is used to eliminate the noise as well as to locate the small reflections in the TDR wave. Results show that the shortened rise time of step wave has a positive effect on the voltage reflection coefficients of the fault, which is conducive to detecting the faults. The recognition capability of the faults can be improved through de-noising and singularity detection by the wavelet method. But as the attenuation and the extension of the rise time of the wave, the method introduced cannot meet completely all the requirements of fault diagnosis. In particular, it is almost impossible to detect the small fault.