EP3158348A1

EP3158348A1 - Method for marking bundles of power lines for diagnosis by reflectometry and corresponding kit

Info

Publication number: EP3158348A1
Application number: EP15733849.2A
Authority: EP
Inventors: Florent LOETE; Michel Sorine
Original assignee: Centre National de la Recherche Scientifique CNRS; Institut National de Recherche en Informatique et en Automatique INRIA; ECOLE SUPERIEURE D'ELECTRICITE
Current assignee: Centre National de la Recherche Scientifique CNRS; Institut National de Recherche en Informatique et en Automatique INRIA; ECOLE SUPERIEURE D'ELECTRICITE
Priority date: 2014-06-20
Filing date: 2015-06-19
Publication date: 2017-04-26
Also published as: CA2952853A1; WO2015193626A1; US10184971B2; FR3022639A1; FR3022639B1; US20170153284A1

Abstract

The invention relates to a method for diagnosis by reflectometry of a bundle of power lines comprising an input point and a plurality of branches, including the following steps: inserting (S50) electric markers having different frequency characteristics onto the branches of the bundle; injecting (S52) a test signal into the bundle from the input point; receiving (S54) a set of reflected signals produced by reflections of the test signal in the branches; analysing all the reflected signals by identifying the markers and by assigning (S56) each reflected signal to one of the branches according to the frequency characteristic of the marker inserted onto said branch; and identifying the presence/absence of a defect in said branch by comparing (S58) the reflected signal assigned to said branch with a reflected signal model obtained by modelling the reflection of the test signal in said branch in the absence of any defect in said branch.

Description

Method of marking electric line bundles for the diagnosis by reflectometry and corresponding kit

FIELD OF THE INVENTION

The present invention relates to the methods of diagnosis by reflectometry, the bundles of power lines and the corresponding kits.

More particularly, the invention relates to a method for the diagnosis by reflectometry of a bundle of electrical lines comprising at least one entry point and a plurality of branches, such a bundle of shaft electrical lines and a diagnostic kit by reflectometry. such a beam.

BACKGROUND OF THE INVENTION

Interconnected complex electronic systems are increasingly present in our daily lives and their failures can have significant consequences in human, economic and social terms, particularly for critical applications of dependability.

It is for this reason that wired interconnection networks are now regarded as critical systems and their diagnosis is just beginning to be seen in the industry.

Indeed, with the increase in cumulative lengths of cables (about 4 km in a modern car and up to 400 km in a civil transport plane) and the evolution of network fault sensitivity due to the complexities of design , various problems due to electric cables can arise at the system level.

The diagnosis of the network is then essential to detect and locate these defects.

Today, for example, a car mechanic can take up to 2 days to find and repair a wiring fault, sometimes after changing components (ECU, connector, etc.) healthy and expensive. For example, it appears that 70% of the computers returned to manufacturers are free from defects.

In the field of aeronautics, the operating loss of an AOG (Aircraft On Ground) because of a breakdown is close to 1 to 2 M € per day.

At present, the most promising technique used for the diagnosis of electrical harnesses or bundles is OTDR.

OTDR is based on a technique similar to that of a radar system.

In particular, a wide spectral band signal is injected into the electrical beam and a part of the signal is reflected towards the injection point by each zone of impedance variation characteristic of the line (discontinuity for example) which is encountered by the signal. Of course, in what follows, the terms "reflected" and "reflected" will be understood as describing one or more electrical signals returned by the transmission medium used to transmit the broadband signal.

This gives a series of echoes whose amplitudes depend on the topology of the beam and any defects therein. The analysis of these amplitudes makes it possible to identify the nature of the defects, that is to say if they are frank defects, for example open circuits or short circuits, or non-free faults ( localized but regular variations of characteristic impedance).

The analysis of the return delay of the echoes at the injection point informs about the position of the defects in the beam.

Thus the document US 2011/0153235 proposes a method for detecting defects in a cabling, by using a graphical modeling of the responses. expected and making a comparison with the responses actually obtained. In FIGS. 8 and 9 of this document, the reference 902 thus indicates a detection of exceeding a difference threshold, representative of a defect. However, in practice, when there is a plurality of beam divisions, there is no guarantee that the fault can be easily located.

In any case, in many cases, there remains an ambiguity regarding the positioning of the defect. For example, if a defect appears beyond a splice, that is to say, beyond a division of the beam into several branches, it is impossible to know simply and quickly which branch it is on. from measurements in one point. This ambiguity constitutes a difficulty during maintenance and repair operations, with an economic stake that may be major for certain areas of application.

The document WO 2010/043602 A1 describes a distributed reflectometry method making it possible to remove the ambiguity of localization of a fault in a complex beam by multiplying the measurement points in the network. More particularly, the complete system of reflectometry (signal generation, acquisition and processing) is duplicated in order to perform a signal injection at the ends of the cable bundle. A diagnosis is made from each end.

In the embedded case, the system is duplicated at each end. In the case of a manual intervention, the ambiguity is lifted only after multiple operations, such as additional dismantling of trim in vehicles by the technician. In addition, this method also requires communication to synchronize the measurements between the different units.

All this translates into a considerable loss of time and money. OBJECTS OF THE INVENTION

The present invention aims to overcome these disadvantages.

For this purpose, a method of the kind in question is characterized in that it comprises the following steps:

insertion of electrical markers on the branches of the beam, the electric markers having different frequency characteristics from each other;

injecting a test signal into the beam from the entry point;

receiving a set of reflected signals produced by reflections of the test signal in the branches of the beam;

analyzing all the reflected signals by identifying the electrical markers and assigning each signal reflected to one of the branches of the beam according to the frequency characteristic of the electric marker inserted on said branch; and

identifying a presence / absence of a fault in said branch by comparing the reflected signal allocated to said branch to a reflected signal model obtained by modeling the reflection of the test signal in said branch in the absence of a fault in said plugged.

Thanks to these arrangements, it is possible to remove the ambiguity of localization of a defect by reflectometry between different branches of a complex topology electrical network, in a simple and inexpensive way, by electrically marking the branches of the network with frequency signatures without disturbing the normal operation of the network.

By electrical marker is meant here a component which may be typically devoid of communication means (without RFID chip, antenna or analog communication circuit) and / or data storage. Electrical markers, passive, perform a simple electrical marking. Such markers can be inserted into the branches when they are not present when the power lines are designed. The term "inserted" for the electrical marker therefore means, obviously, that the latter is added between two successive sections of the branch or at one end so as to extend this branch.

In various embodiments of the method according to the invention, one or more of the following provisions may also be used:

the electrical markers comprise passive and / or active linear and / or non-linear electric dipoles and / or quadrupoles;

the electric markers comprise low-pass filters;

at least some of the low pass filters have different cutoff frequencies;

at least some of the low pass filters have different cutoff slopes;

at least some of the low pass filters are low pass filters of the order ^1;

at least some of the low pass filters are low pass filters of ^2nd order;

the injection step is implemented by a test signal generation module comprising a digital-to-analog converter and an injection coupling element; and

the receiving step is implemented by an electrical signal detection module comprising a reception coupling element and an analog-digital converter.

The invention also relates to a bundle of electrical lines comprising at least one entry point and a plurality of branches, characterized in that it comprises a plurality of electrical markers each inserted on a branch of the beam, the electrical markers having different frequency characteristics from each other.

In various embodiments of the beam according to the invention, it may optionally be resorted further to one and / or the other of the following provisions:

each electrical marker has an impedance equal to a characteristic impedance of the branch on which it is inserted, at least for electrical signal frequencies corresponding to service frequencies of the beam (Σ); and

the beam is a land vehicle, air, space or maritime or river transport vehicle equipment, arranged for its service operation on board said vehicle.

The invention further relates to a diagnostic kit by reflectometry of a bundle of electrical lines comprising at least one entry point and a plurality of branches, characterized in that it comprises:

a plurality of electrical markers each adapted to be inserted on a branch of the beam (Σ), the electrical markers having different frequency characteristics from each other;

a test signal generating module adapted to be connected to the entry point and to inject a test signal into the beam from the entry point;

an electrical signal detection module adapted to be connected to the input point and to receive a set of reflected signals produced by reflections of the test signal in the branches of the beam; and

a processing module adapted to be connected to the detection module and to analyze the whole signals reflected by identifying the electrical markers and assigning each reflected signal to one of the branches of the beam according to the frequency characteristic of the electric marker inserted on said branch, and to identify a presence / absence of a defect in said branch comparing the reflected signal assigned to said branch to a reflected signal model obtained by modeling the reflection of the test signal in said branch in the absence of a fault in said branch.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood on reading the following description of one of its embodiments, given solely by way of nonlimiting example with reference to the appended drawings, in which:

- Figure 1 is a diagram illustrating a diagnostic device reflectometry according to the invention;

Fig. 2 is a diagram showing a frequency characteristic of an electrical marker of the device of Fig. 1; and

Figure 3 is a diagram illustrating the various steps of a diagnostic method by reflectometry according to the invention.

DESCRIPTION DETAILED

In the various figures, the same references designate identical or similar elements.

Figure 1 illustrates a device 10 diagnostic reflectometry of a beam Σ of power lines.

The beam Σ has a complex topology and comprises at least one entry point 12 and a plurality of branches 14.

Each branch 14 is connected to a system Σ ' _x having an own input impedance Z _x .

The device 10 comprises a plurality of electrical markers TAG _X each inserted on one of the branches 14 of the beam Σ.

Each electrical marker TAG _X has a frequency characteristic, or frequency signature, known to it, all the frequency characteristics being different from each other.

In particular and as represented in FIG. 2, each electrical tag TAG _X has an impedance Z _TAGx equal to a characteristic impedance Z _c of the branch 14 on which it is inserted, at least for frequencies f of the electrical signal corresponding to the frequencies of service f _ser v beam Σ. Thus, the presence of electrical markers TAG _X does not disturb the useful signals that are conveyed by the beam Σ during a use thereof which corresponds to its service function.

In other words, the impedance Z _TAGx is adapted to the characteristic impedance Z _c of the branch 14 on which it is inserted, on the useful frequency band (s).

In other words again, the electrical markers TAG _X are "transparent" on the spectral band (s) of the useful signals of the beam Σ.

As a variant, the impedance Z _TAGx of the electrical marker TAG _X may be equal to an impedance of an input stage of the system Σ ' _x at the frequencies of the useful signals of the beam Σ.

The electrical markers TAG _X may comprise dipoles and / or passive and / or active linear and / or non-linear electrical quadrupoles, in particular filters. It is understood that the electrical markers may be devoid of auxiliary power source (passive markers case).

For the applications envisaged here, the useful signals are generally low or medium frequency signals. TAG _X Electric markers may thus comprise low-pass filters, e.g., low-pass filters of the ^1st order and low-pass filters of ^2nd order and generally of low-pass filters of ^nth order.

Even more generally, electrical markers may include any filter whose presence is detectable.

In order to differentiate them from each other, at least some of these low pass filters may have different cutoff frequencies and / or different cutoff slopes. In Figure 2, f _c represents the cutoff frequency of low pass TAG _X. This cut-off frequency f _c is different from the service frequencies f _ser v of the beam Σ.

The electrical markers TAG _X can be inserted anywhere on the corresponding branch 14, for example at the beginning, in the middle, at the end or else be integrated in the input stage of the corresponding system Σ ' _x .

In FIG. 1, the electrical markers TAG _X are inserted on the last branches 14 of the bundle Σ, but it is of course possible to insert them on any branches, for example on the last-to-last branches and more generally on the _^nth branches of the Σ beam. In these cases, we do not isolate the systems Σ ' _x individually but we isolate sets of systems Σ' _x .

The device 10 further comprises a test signal generation module adapted to be connected to the input point 12 and to inject a test signal into the beam Σ from the input point 12.

The production module 20 comprises, for example, a digital-to-analog converter DAC connected to an injection coupling element 22 itself connected to the entry point 12. The test signal is a multifrequency signal with a broad spectral band, typically a pulse. The test signal advantageously has nonzero spectral components in an extended spectral range which contains the cutoff frequencies of all electrical markers.

The device 10 further comprises an electrical signal detection module adapted to be connected to the input point 12 and to receive a set of reflected signals produced by reflections of the test signal in the branches 14 of the beam Σ.

The detection module 30 comprises, for example, a reception coupling element 32 connected to the entry point 12 and an analog-digital converter ADC connected to the reception coupling element 32.

The device 10 also comprises a processing module 40 adapted to be connected to the detection module 30 and to analyze all the reflected signals.

The invention relates both to embedded devices and landed devices.

The on-board device comprises at least the beam Σ provided with the entry point 12 and the branches 14, and the electrical markers TAG _X inserted permanently on the branches 14.

This may include land vehicle (automobile, bus, etc.), air (airplane, helicopter, etc.), space (rocket, satellite, etc.) or marine (surface) vehicle equipment. or submarine) or fluvial.

The disembarked device may consist of a reflectometry diagnostic kit comprising the electrical markers TAG _X , the production module 20, the receiving module 30 and the processing module 40.

With reference to Figure 3, the method of OTDR diagnosis includes the following steps.

A first step S50 consists of inserting the electrical markers TAG _X on the branches 14 of the bundle Σ.

It should be noted that when it is an embedded device, this step has already been implemented during the manufacture or installation of the beam Σ in the vehicle.

Then, in a step S52 implemented by the production module 20, a test signal is injected into the beam Σ from the entry point 12.

Part of the test signal is then reflected in the different branches 14 thus generating reflected signals.

All of these reflected signals are then received by the detection module 30 in a step S54, then analyzed by the processing module 40.

In particular, the processing module 40 identifies the electrical markers and assigns, in a step S56, each signal reflected at one of the branches 14 according to the frequency characteristic of the electrical marker TAG _X inserted on this branch 14.

The processing module 40 then compares, in a step S58, each reflected signal assigned to a branch 14 to a corresponding signal model obtained by modeling the reflection of the test signal in the corresponding branch 14 in the absence of a fault in this branch. 14.

The model of course takes into account the frequency signatures of TAG _X electrical markers and the complex du beam topology.

Depending on the results of this comparison, it is then possible to identify the presence or absence of a fault in the branch 14. The invention therefore proposes a method and devices, on-board or off-shore, simple to implement and inexpensive, to unambiguously identify and locate a fault in a line by electrically marking each of the branches using filters. of an electrical beam with a particular frequency signature.

In addition, the electrical markers considered in the present invention do not disturb the useful signals carried by the beam.

The more the structure of the markers is complex, or in other words the more the frequency signature of the markers is specific, the easier it will be to assign the reflected signals to the respective branches. The cost of a filter depends on its complexity but nevertheless remains much lower than that of a complete OTDR system.

The invention applies in particular to electrical harnesses having a critical role from an operational safety point of view, particularly in the field of transport (automotive but especially aeronautical), nuclear power and public networks (monitoring the theft of cables ).

Of course, the invention can be applied to perform a diagnosis when an incident is detected in the network or simply to carry out a diagnosis of monitoring the state of the network.

The analysis of the reflected signals which is carried out by the processing module has been described above in the frequency domain (FDR for Frequency Domain Reflectometry). In such a spectral analysis, the reflection coefficient at the point of entry of the beam, and therefore at the injection point of the test signal, is affected by the frequency signatures of the electrical markers.

But the processing module can perform equivalent way a temporal analysis of the reflected signals (TDR for Time Domain Reflectometry). In this case, each echo from a marked branch is convoluted by the impulse response of the corresponding electrical marker. The transition from one to the other and vice versa is done by inverse Fourier transform and Fourier transform respectively.

Those skilled in the art will understand that the invention results from the principle of inserting different markers in separate branches of the beam, so that the signal which is reflected by one of the branches can be identified as coming undoubtedly from this branch. . The eventual alteration of the reflected signal then reveals a defect present in this branch. However, the invention is compatible with several modes of analysis of reflected signals, which the skilled person can implement without difficulty.

Claims

Method for the diagnosis by reflectometry of a bundle (Σ) of electrical lines comprising at least one entry point (12) and a plurality of branches (14), characterized in that it comprises the following steps:

insertion (S50) of electrical markers (TAG _X ) on the branches (14) of the beam (Σ), the electric markers (TAG _X ) having different frequency characteristics from each other;

injecting (S52) a test signal into the beam (Σ) from a determined entry point (12);

receiving (S54), at the determined entry point (12) side, a set of reflected signals produced by reflections of the test signal in the branches (14) of the beam (Σ);

analyzing all the reflected signals by identifying the electrical markers (TAG _X ) and assigning (S56) each reflected signal to one of the branches (14) of the beam (Σ) according to the frequency characteristic of the electrical marker ( TAG _X ) inserted on said limb (14); and

identifying a presence / absence of a fault in said branch (14) by comparing (S58) the reflected signal assigned to said branch (14) to a reflected signal model obtained by modeling the reflection of the test signal in said branch (14) in the absence of a fault in said branch (14).

2. Method according to claim 1, wherein the electrical markers (TAG _X ) comprise dipoles and / or passive and / or active linear and / or nonlinear electric quadrupoles.

The method of claim 1 or 2, wherein the electrical markers (TAG _X ) comprise low-pass filters.

4. The method of claim 3, wherein at least some of the low pass filters have cutoff frequencies (f _c) different.

The method of claim 3 or 4, wherein at least some of the low pass filters have different cutoff slopes.

6. A method according to any one of claims 3 to 5, wherein at least some of the low pass filters are low pass filters of the order ^1.

7. A method according to any one of claims 3 to 6, wherein at least some of the low pass filters are low pass filters of ^2nd order.

The method according to any one of claims 1 to 7, wherein the injecting step is implemented by a test signal generation module (20) comprising a digital-to-analog converter (DAC) and an element. injection coupling (22).

The method according to any one of claims 1 to 8, wherein the receiving step is implemented by an electrical signal detection module (30) comprising a receiving coupling element (32) and an analog converter. -digital (ADC).

10. Beam (Σ) of power lines having at least one entry point (12) and a plurality of branches (14), characterized in that it comprises a plurality of electrical markers (TAG _X ) each inserted on one of the branches (14) of the beam (Σ), the electrical markers (TAG _X ) having different frequency characteristics from each other, which make it possible to characterize one branch with respect to the others in internal beam reflections induced by an injected test signal from a given point during a diagnosis by reflectometry, each of the electrical markers (TAG _X ) being preferably chosen from the group which gathers: the dipoles and / or the linear electric quadrupoles and / or non-linear passive and / or active; and

- the low-pass filters.

A harness (Σ) according to claim 10, wherein each electrical marker (TAG _X ) has an impedance (Z _TAGx ) equal to a characteristic impedance (Z _c ) of the branch (14) on which it is inserted, at least for frequencies (f) of electrical signal corresponding to service frequencies (f _ser v) of the beam (Σ).

12. Beam (Σ) according to claim 10 or 11, the beam (Σ) being a land vehicle equipment, air, space or maritime transport vehicle or fluvial, arranged for its service operation on board said vehicle.

13. Diagnostic kit by means of a beam (Σ) of electrical lines comprising at least one entry point (12) and a plurality of branches (14), characterized in that it comprises :

a plurality of electrical markers (TAG _X ) each adapted to be inserted on one of the branches (14) of the beam (Σ), knowing that the electrical markers (TAG _X ) have different frequency characteristics from each other and are adapted to transfer a signature in reflected signals produced in the branches (14) by reflections of a test signal during a diagnosis by reference, each of said electrical markers being preferably selected from the group which gathers:

the passive and / or active linear and / or nonlinear electric dipoles and / or quadrupoles; and

- low-pass filters;

a test signal generating module (20) adapted to be connected to a determined input point (12) and for injecting a test signal into the beam (Σ) from the determined entry point (12);

a signal detection module (30) electrical apparatus adapted to be connected to the determined input point (12) and to receive a set of reflected signals produced by reflections of the test signal in the branches (14) of the beam (Σ); and

a processing module (40) adapted to be connected to the detection module (30) and for analyzing all the reflected signals by identifying the electrical markers and assigning each reflected signal to one of the branches (14) of the beam ( Σ) according to the frequent characteristic of the electrical marker

(TAG _X ) inserted on said branch (14), and for identifying a presence / absence of a fault in said branch (14) by comparing the reflected signal allocated to said branch

(14) to a reflected signal model obtained by modeling the reflection of the test signal in said branch (14) in the absence of a fault in said branch (14).