Master of Science

thesisThe focus of this thesis is the impact and use of crosstalk and coupling when testing for electrical wiring faults using reflectometry. This thesis describes a method for detecting and locating faults on cable shields using an adapted reflectometry system. A signal transmitted on the inner conductor is coupled to the outside through the fault, a small aperture in the cable shielding. This very small signal is then detected and correlated with the original signal transmitted on the inner conductor. The signals that leak out of the aperture, the damaged shield, and propagate down the outside of the cable are quantified as a function of the aperture size and frequency. A ferrite loaded toroidal sensor design is also proposed for receiving this external signal in order to both detect and localize the shield damage. Both simulations and measurements validate the effectiveness of this method. Unshielded discrete wires are another common type of transmission line. While unshielded wires are primarily used for DC power, they are still subject to degradation over time and require maintenance. Unlike shielded cables, there is a significant amount of coupling that occurs between adjacent wires during a reflectometry test. This coupling is quantified and evaluated for two applications. The first is simultaneous testing of multiple adjacent wires in a bundle. In this case, minimizing the coupling is desirable in order to reduce noise in the reflectometry signature. The second is the exploration of the potential for a single reflectometry test to locate faults on adjacent wires without directly testing them. When a single test is performed in a multiwire bundle, the reflectometry signature will be a superposition of reflections from all nearby conductors. This thesis addresses the testing of a multiconductor wiring structure with a common signal reference as well as a similar structure with an isolated signal reference. In order to accurately detect faults on multiconductor wiring structures, both testing methods must be considered. A fault between a conductor and its reference conductor is easily detectable. A cross fault between two nonreference conductors is not. For cross fault consideration, the only method for detection is using a common signal reference and analyzing the data on adjacent lines

Theory and application of time-frequency analysis to transient phenomena in electric power and other physical systems

textThis dissertation provides a new theoretical scheme of signal processing: cross time-frequency analysis. The proposed cross time-frequency analysis is applied to various types of real-world signals and systems in order to verify the feasibility and applicability of the proposed theory. The application of time-frequency analysis is focused on electric power and other physical systems. Unfortunately, classical Fourier-based methodologies and power quality indices are not directly applicable for the assessment and localization of transient power quality phenomena. Hence, in this dissertation, application of time-frequency analysis is discussed for the assessment and localization of transient power quality events. Through the use of joint time and frequency localized “energy” distributions, a set of time-frequency based transient power quality indices are presented and applied to real-world disturbance signals. Also, a solution for the spatial localization of transient disturbances is presented. It rests upon calculating a time and frequency localized “phase difference” via cross time-frequency analysis. By evaluating the phase difference of voltage and current at the time and frequency of interest and at different spatial points, one can identify the direction of transient disturbance energy flow in order to pinpoint the location of the transient disturbance source. In addition, applications of time-frequency theory have been extended to various types of real-world physical signals and systems. A new reflectometry methodology, time-frequency domain reflectometry, is proposed and demonstrated with experimental results. Also, cross time-frequency analysis has been utilized for the characterization of ocean wave group propagation, and applied to transient postural sway signals to identify the effects of aging and sensory systems on human postural control systems.Electrical and Computer Engineerin

Locating Multiple Soft Faults in Wire Networks Using An Alternative DORT Implementation

International audienceDecomposition of the time reversal operator (DORT) was recently applied to the problem of detection and location of soft faults in wire networks and proved effectual when dealing with a single fault, even in the case of complex network configurations. In this paper, the case of location of multiple faults is addressed, first proving that the standard DORT formulation does not allow to take a clear decision about the individual position of each fault. An alternative version of the DORT, based on an updating procedure, is presented and demonstrated to enable accurate and selective location of multiple soft faults. The proposed procedure is also shown to allow estimating the reflection coefficient of each fault, thus giving access to their severity

Enhanced TDR Technique for Fault Detection in Electrical Wires and Cables

Degradation and failure of aircraft wiring insulation is of particular interest which could lead to smoke and fire due to arcing. With two recent major air accidents and hundreds of major incidents over the past twenty years, health monitoring and sustainment of wiring, particularly for aging aircraft is a major concern. The results of a technique based on TDR, using trains of successive pulses is presented in this paper for detection of partial damage to insulation in electrical wires and cables

Fault Detection in Aircraft Wiring using Enhanced multi-pulse TDR Technique

Defects in electrical wiring could result in disastrous consequences especially in airborne systems. The defects may in many cases be due to minor damage in the insulation or shielding of wires and cables. This type of defect is not usually detected using routine testing. They may be caused by vibration, moisture, heat, cold, abrasion and other similar effects, causing frays and cracking in wire insulation. Degradation and failure of aircraft wiring insulation is of particular interest which could lead to smoke and fire due to arcing. Results of a technique based on TDR, using trains of successive pulses was previously presented and confirmed through modelling of cables. In this paper the investigation is extended to include small 10 mm and 5 mm holes in coaxial and shielded twisted pair cables. The technique is easy to establish and due to its cumulative nature, can provide higher accuracy with increasing incremental steps. It also holds promise for detection of stray fields for non-contact detection of faults, particularly in shielded cables and wires

Novel Reflectometry Method Based on Time Reversal for Cable Aging Characterization

International audienceThis paper investigates the effects of aging on electrical cable characteristics and proposes a new method for detecting and characterizing cable aging (i.e. homogeneous slow degradation) based on time reversal. In case of a global cable aging, the commonly used methods such as reflectometry provide non-relevant or inaccurate information. Through theoretical study and numerical simulations, the benefits of this new method called Time Reversal Reflectometry (TRR) are presented. TRR is experimentally shown to be successful for the detection and quantification of cable aging