Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/08—Locating faults in cables, transmission lines, or networks
  • G01R31/11—Locating faults in cables, transmission lines, or networks using pulse reflection methods
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/08—Locating faults in cables, transmission lines, or networks
  • G01R31/088—Aspects of digital computing

Definitions

• a calculation of average MOY is carried out before COR correlation.
• FIG. 2 shows an example of a stationary reference signal S S T having a predetermined period T.
• This signal is continuously injected into the cable L.
• M a continuous measurement or acquisition of the signal is carried out M s feeds back.
• an oversampling of the signal is performed by shifting the sampling clock of the ADC digital analog converter every T or multiple periods of this period T.
• the over-sampled stationary signal is then reconstituted.
• SREC- The calculation of average MOY is applied over several periods of the oversampled stationary signal SREC.
• four acquisition periods A 1 , A 2 , A 3 , A 4 and an average of two acquisitions are considered.
• the second fault D2 appears at the same time as D1 but has a longer duration which makes the signature of the defect extends over the two acquisitions Ai and A 2 .
• This second fault D2 can be detected with a higher probability than the first fault D1.
• This implementation requires a memory capable of containing N * P * W bits, with N the number of points of a period of the stationary signal, P the number of over-sampling phases and W the number of bits on which a sample is quantified. for example equal to 16 bits.
• This solution not only does not detect defects of short duration but also requires a large memory space to perform the averaging.
• a first memory MEMi makes it possible to store N.P samples of the reconstituted signal corresponding to a period of the stationary signal.
• the invention also aims to detect defects related to anomalies that are harmful for the system under test.
• a reflectometry test system used to diagnose a driver associated with a complex system may produce alarms for intermittent faults that are caused, for example, by vibrations.
• the invention aims to solve this limitation by the implementation of one or more filter (s) adapted (s) to the defects that it is precisely desired to detect, for example defects originating as a harmful phenomenon at a given frequency .
• the invention also makes it possible to ignore or discriminate other frequencies which correspond to vibratory phenomena judged to be non-harmful or normal.
• the subject of the invention is a method for detecting an intermittent fault in a transmission line comprising the following steps:
• said at least one filter is determined at least from the following steps:
• the step of analyzing said at least one temporal reflectogram comprises: the search for at least one amplitude peak characteristic of the signature of an intermittent fault,
• said at least one filter is an infinite impulse response filter.
• the method according to the invention comprises the steps of:
• the method according to the invention comprises a step of generating and injecting the reference signal into the transmission line.
• the subject of the invention is also a system for detecting an intermittent fault in a transmission line comprising a measurement device able to acquire, at a point on the line, a temporal measurement of a reference signal previously injected into the transmission line. line, reflected on a singularity of the line and retro-propagated towards said point and:
• At least one device for filtering the temporal measurement of the signal using at least one predetermined filter as a function of the spectral signature of a given type of defect at least one device for filtering the temporal measurement of the signal using at least one predetermined filter as a function of the spectral signature of a given type of defect
• At least one device for calculating the intercorrelation between at least one filtered signal and the reference signal for producing at least one temporal reflectogram a device for analyzing said at least one temporal reflectogram to characterize the possible presence of at least one intermittent fault on the transmission line.
• the invention also relates to a computer program comprising instructions for executing the method of detecting an intermittent fault in a transmission line according to the invention, when the program is executed by a processor.
• the subject of the invention is also a recording medium readable by a processor on which is recorded a program comprising instructions for performing the method of detecting an intermittent fault in a transmission line according to the invention, when the program is executed by a processor.
• FIG. 1 a diagram of a wiretap diagnostic system by reflectometry according to the prior art
• FIG. 3 a diagram of a possible implementation of an average calculation as envisaged in a system of the prior art
• FIG. 4 a diagram of a possible implementation of a sliding average calculation as envisaged in a system of the prior art
• FIG. 5a a diagram of an intermittent fault detection system according to the invention
• FIG. 5b a diagram of an alternative embodiment of the system of FIG. 5a
• FIG. 6a an example of a time signal reflected on an intermittent vibratory type fault
• FIG. 6b an example of a time signal reflected on an intermittent defect of the default type
• FIG. 7b is a diagrammatic representation of the time response and the frequency response of an intermittent defect of the default type
• FIG. 8a a flowchart representing the steps necessary to determine the parameters of the filter to be used in a system according to the invention
• the invention proposes to replace the average calculation MOY by a filter adapted to the characteristics of the intermittent defect that one wishes to detect.
• the part of the system 500 which concerns the generation and the injection of the signal may be distinct from the part of the system 500 which concerns the acquisition of a measurement of the reflected signal and the processing relating to the filtering and cross correlation calculation to produce a reflectogram R (t).
• two separate LC couplers can be used, the first for the injection, at a first point of the line L, of the reference signal and a second for the measurement, at a second point of the line L, of the retro signal. -propagé.
• the parameters of the filter determined by the controller CTRL include in particular the bandwidth or the coefficients of the filter.
• the parameters of the filter are determined according to the spectral or temporal signature of the intermittent fault that one wishes to detect.
• the system according to the invention may comprise several FIL filters instead of just one as shown in FIG. 5a, each filter being set to be adapted to the detection of a particular type of defect.
• each of the filters is controlled by the control member CTRL whose particular role is to select one of several available filters, depending on the type of defect to be detected.
• the n filters associated with the n correlators operate in parallel.
• the digitized signal at the output of the ADC converter is processed in parallel by the n filters and n correlators.
• Each of the filters can be configured to detect a particular fault.
• each filter is different and has a response configured according to the characteristics of a particular fault.
• An advantage of this variant is that it makes it possible to detect several different types of faults simultaneously.
• a controller CTRL (not shown in Figure 5b) can be used to configure the type of filter implemented in each filter device.
• Another advantage of this variant is that it makes it possible to follow the revolution of a defect in time. For example, a scalable tear in a conductor causes a change in its own resonance frequency. With the system of FIG. 5b, it is possible to follow the evolution of such a defect by configuring the passbands of the different filters so that each filter is able to discriminate the resonance frequency of the vibration induced by the defect. at one moment of its evolution.
• Another advantage of this variant is that it allows parallel detection of several different types of defects.
• This aspect of the invention makes it possible in particular to discriminate the spectral signature from a defect which would be masked by that of another defect. This also allows tracking of corrective actions taken to correct the defect.
• Filters FIL1, FIL2, ..., FILn can be implemented in time or frequency form.
• FIG. 6a schematically represents the influence, on a temporal signal injected in a transmission line, of the reflection of this signal on an intermittent vibratory type fault, for example resulting from a short-circuit, an open circuit or a fault generated by the vibrations of a device.
• FIG. 6a only shows the influence of the fault on the reflected signal, the reflected signal itself being dependent on the type of signal injected into the line.
• the signal reflected on the singularity created by the defect is modulated by the estimated time response of the defect.
• the influence of an intermittent vibratory type fault can be modeled by a signal sinusoidal duration T d equal to the duration of the fault.
• the sinusoidal signal has a resonant frequency of its own. Its envelope may be oval, as shown in Figure 6a, or rectangular, or logarithmic or another form.
• FIG. 6b represents the influence of another type of fault, this time it is an intermittent defect type franc defect, whose time response can be modeled by a time slot (or door function) of duration T d equal to the duration of the fault.
• FIGS. 6a and 6b relate to two types of intermittent faults, but other intermittent faults can be envisaged insofar as one is able to measure or estimate their temporal response, ie the influence of such a fault on a signal propagating in the transmission line and reflecting on the impedance discontinuity caused by the fault.
• Figure 7a shows two diagrams schematizing respectively the temporal response of an intermittent vibratory defect (figure above) and its frequency response (bottom figure).
• FIG. 7a At the top of FIG. 7a, there is shown a modeling of the temporal response of an intermittent vibratory defect of duration T d .
• FIG. 7a On the bottom of Figure 7a, there is shown the frequency transformation of the time response, obtained for example by a discrete Fourier Transform.
• FIG. 7b represents, in the same way, the temporal response
• FIG. 8a represents, on a flowchart, the steps of a method for determining the parameters of the FIL filter used in a system according to the invention.
• the method receives as input the default type intermittent that one wishes to be able to detect, for example a defect franc or a vibratory defect.
• a first step 801 it is estimated the frequency response of the defect, that is to say the spectrum of the signal generated by the appearance of the defect, also called spectral signature of the defect.
• the expression "spectral signature of a defect” means the influence, in the frequency response or the spectrum, of the signal reflected on a defect, of the defect itself, this influence varying according to the nature of the defect, notably the type of defect (free or vibratory) and its duration.
• the signal injected into the cable is reflected on the impedance discontinuity created by the fault, it is retro-propagated by being modified by the influence of the fault.
• a first step 810 the time response h (t) of the fault is estimated from the type of fault that it is desired to detect.
• the impulse response of the filter is determined to be the complex conjugate h * (-t) of the temporal response h (t) determined in step 810.
• the filter coefficients from its impulse response and choosing the filter order.
• the coefficients of the filter are determined from its impulse response using any method or algorithm of numerical resolution known to those skilled in the art, for example with the aid of the Steiglitz-McBride algorithm described in "A technique for identification of linear systems, K. Steiglitz and McBride, IEEE trans. Auto. con., vol. AC-10, pp. 461-464, Oct. 1965 ".
• the filter used is preferably a low pass or bandpass filter, in order to filter the high frequency disturbances. It is more generally a suitable filter.
• the choice of the bandwidth of the filter results in particular from a compromise between the accuracy of detection of a particular defect and the level of filtered noise.
• a narrow bandwidth generates a lower detection gain but a lower noise level after filtering as well.
• a larger bandwidth generates a noise level after high filtering but a higher detection gain because the amplitude of the signature of the defect to be detected is amplified.
• the bandwidth of the filter is preferably centered on the resonance frequency of the fault.
• FIG. 9 summarizes the implementation steps of the method for detecting an intermittent fault according to the invention.
• a reference signal is injected at an injection point of a transmission line L. This step is not considered in the case where it is only from the point of view of the executed method by a system 500 which does not include the part relating to the generation and injection of the signal, part implemented in a separate system.
• step 901 the retro-propagated signal in line L is measured at a measurement point.
• a filtering parameterized according to the type of fault to be detected, is applied to the measured signal.
• 903 is calculated, the cross-correlation between the filtered signal and the signal generated before injection.
• a diagnosis is made as to the presence of a defect and its measured position on the reflectogram R (t) resulting from the cross correlation calculation in step 903.
• the result of the diagnosis can be provided to a user through a display interface.
• the displayed result may include an indication of the presence of a fault on the line and / or an indication of the position of the fault on the line.
• the system according to any one of the embodiments of the invention may be implemented by an electronic card on which the various components are arranged.
• the card can be connected to the cable to be analyzed by a CPL coupling means which can be a directional coupler with capacitive or inductive effect or an ohmic connection.
• the coupling device can be made by physical connectors which connect the signal generator to the cable or by non-contact means, for example by using a metal cylinder whose internal diameter is substantially equal to the outer diameter of the cable and which produces an effect Capacitive coupling with the cable.
• the method according to the invention in particular the correlator COR and the FIL (s) FIL (s) can be implemented in an embedded processor or not or in a specific device.
• the processor may be a generic processor, a specific processor, an application-specific integrated circuit (also known as ASIC for Application-Specifies Integrated Circuit) or an in-situ programmable gate array (also known as the English name of FPGA for "Field-Programmable Gâte Array ").
• the device according to the invention can use one or more dedicated electronic circuits or a general purpose circuit.
• the technique of the invention can be realized on a reprogrammable calculation machine (a processor or a micro-controller for example) executing a program comprising a sequence of instructions, or on a dedicated computing machine (for example a set of doors as an FPGA or an ASIC, or any other hardware module).
• a reprogrammable calculation machine a processor or a micro-controller for example
• a dedicated computing machine for example a set of doors as an FPGA or an ASIC, or any other hardware module.
• the reference to a computer program that, when executed, performs any of the functions described above, is not limited to an application program running on a single host computer.
• the terms computer program and software are used herein in a general sense to refer to any type of computer code (for example, application software, firmware, microcode, or any other form of computer code).
• computer instruction that can be used to program one or more processors to implement aspects of the techniques described herein.
• the means or computer resources can be distributed (“Cloud Computing"), possibly using peer-to-peer technologies.
• the software code may be executed on any suitable processor (for example, a microprocessor) or a processor core or set of processors, whether provided in a single computing device or distributed among a plurality of computing devices (eg example as possibly accessible in the environment of the device).
• the executable code of each program allowing the programmable device for implementing the processes according to the invention can be stored, for example, in the hard disk or in read-only memory.
• the program or programs may be loaded into one of the storage means of the device before being executed.
• the central unit can control and direct the execution of instructions or portions of software code of the program or programs according to the invention, instructions that are stored in the hard disk or in the ROM or in the other storage elements mentioned above.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Mathematical Physics (AREA)
• Theoretical Computer Science (AREA)
• Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
• Monitoring And Testing Of Transmission In General (AREA)

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• 2017
  • 2017-04-19 FR FR1753368A patent/FR3065534B1/fr active Active
• 2018
  • 2018-04-18 US US16/605,795 patent/US20200124656A1/en not_active Abandoned
  • 2018-04-18 WO PCT/EP2018/059836 patent/WO2018192939A1/fr unknown
  • 2018-04-18 EP EP18720178.5A patent/EP3612849A1/de not_active Withdrawn

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