Aging Wire Fault Diagnosis Using Faster, Higher-Precision Methods

This paper presents novel implementation of forward and inverse methods for locating faults in the shields of coaxial cable and other shielded lines. In accomplishing these tasks, direct and probabilistic inversion methods are used to estimate fault and wire parameters. Some numerical finite-difference techniques are capable of modeling the characteristic impedance of a chafe one frequency at a time or without consideration of frequency dependence. Other more computationally expensive software takes frequency into account. By simulating limited number of points, we can use a curve fitting technique to predict the chafe profile and thus save time in the long run. The ABCD forward method also provides a quick and yet realistic solution to the transmission modeling, making modeling a cascaded transmission line system easily done by connecting the modulized blocks. With the success of the forward modeling method, the inversion can be benefited from it. Iterative inversion methods are capable of recovering multiple unknown parameters (lengths and impedances) by approaching the result gradually. Gradient inversion and maximum a posteriori (MAP) inversion results for fault location and size were found to be accurate. A simple and yet effective wire fault profile building technique are also presented. Finally, a novel method of external field measurement from small chafe holes is presented. These new methods prove highly useful for simulation and analysis of complex systems. Thus, faults can be accurately identified, located, and diagnosed with high precision, providing real solutions for greater safety and reparability in aerospace wiring systems. Location and diagnosis of faults in aging electrical wiring can enable their timely repair, thus preventing costly and potentially hazardous post-failure repairs.