Locating Faults With High Resolution Using Single-Frequency TR-MUSIC Processing

Abstract

Time-Reversal multiple signal classification (TR-MUSIC) is here applied to testing cable networks in order to detect and locate soft faults. TR-MUSIC is shown to provide spatial resolution in the millimeter range while using continuouswave (CW) test signals, even at frequencies with guided wavelengths much larger than cables length. State of the art timedomain reflectometry (TDR) methods would require bandwidths in the order of hundreds of MHz for a similar performance. As opposed to TDR, TR-MUSIC does not suffer from the ambiguity created by the existence of multiple echoes in cable networks, which can be easily misinterpreted as multiple faults, leading to false alarms. TR-MUSIC is intrinsically adapted to dealing with multiple faults, handing a direct estimate of the number of faults found in a network under test. Furthermore, the detection capabilities of TR-MUSIC are insensitive to the severity of a fault, as faults are not detected based on the intensity of their echoes as done in TDR techniques, but on a sub-space approach mostly dependent on phase patterns. Accurate identification of faults from CW signals points to the possibility of designing simpler test systems, not requiring pulse generators and fast electronics. TR-MUSIC accuracy is demonstrated experimentally for locating both single as well as multiple soft faults in two cable networks. The proposed method also gives access to the reflection coefficient of each fault, thus enabling an estimate of its severity.

Multifrequency TR-MUSIC Processing to Locate Soft Faults in Cables Subject to Noise

“…The basic operations involved in the use of TR-MUSIC technique in fault location, are here recalled; the interested Reader should refer to [16] for more details. All quantities in the following are functions of the frequency ν; it might be dropped for the sake of brevity.…”

“…1), where the pseudo-spectrum presents a single peak. In [16], it was proved that TR-MUSIC can still provide sub-millimeter resolution even when applied to such relatively low test frequencies.…”

“…While most techniques rely on the use of wide-band excitation signals [3], [8]- [15], it has recently been demonstrated [16] that soft faults can be located by using single-frequency continuous-wave tests, and still obtain sub-millimeter precision, thanks to the super-resolution properties of time reversalbased multiple signal classification (TR-MUSIC) [17]. In particular, test signals below 10 MHz were shown in [16] to result in estimates of fault locations within a few millimeters, i.e., about 1/20000 of wavelength of the test signal. Similar spatial M. Kafal is with the Laboratory of Reliability and Integration Sensors (LFIC) at the French Alternative Energies and Atomic Energy Commission (CEA) A. Cozza is with the Group of Electrical Engineering -Paris (GeePs), Cen-traleSupelec, Univ.…”

Frequency Selection for Reflectometry-Based Soft Fault Detection Using Principal Component Analysis

“…In fact, the propagation velocity (7) and the spatial resolution (8) enabled by a test signal vary with the frequency as shown [9]:…”

A Statistical Study of DORT Method for Locating Soft Faults in Complex Wire Networks

“…Based on a radically different concepts, time-reversal (TR)-based methods originally developed in acoustics as remote sensing techniques [4] have shown to be effectual in locating soft faults in complex branched wire networks [5]- [8]. For instance, decomposition of the TR operator (DORT), a computational TR method, relies on the analysis of the network's TR operator (TRO) in an effort to synthesize customized testing signals.…”