Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M7/00—Vibration-testing of structures; Shock-testing of structures
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
  • G01H1/00—Measuring characteristics of vibrations in solids by using direct conduction to the detector
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
  • G01H11/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties
  • G01H11/06—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties by electric means
  • G01H11/08—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties by electric means using piezoelectric devices
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
  • G01M5/0025—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings of elongated objects, e.g. pipes, masts, towers or railways
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
  • G01M5/0066—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by exciting or detecting vibration or acceleration

Definitions

• the invention relates to the detection of a state or a malfunction of an assembly comprising a structure, in particular by means of a system comprising at least one vibration sensor.
• the present invention comprises the capture of a signal constituted by the vibrations of the structure, in particular with a view to enabling the detection and categorization of a state or a malfunction of said assembly.
• the present invention aims a system for detecting a state or a malfunction of an assembly comprising a structure through a vibration analysis of said structure.
• the proposed system in its various variants, is applicable in many fields, including the monitoring of a network of overhead power lines, a vehicle structure, for example an aircraft, or a network. of railways.
• the particular case of an implementation for detecting a state or a malfunction in a network of overhead power lines is described more precisely below.
• the network of overhead power lines necessary for this routing forms a network of the territory, an architecture composed of supporting structures - in other words towers - and electric cables.
• this network of overhead power lines has a total length of more than one million kilometers.
• Monitoring and Early detection of potential malfunctions is a crucial issue for securing electricity distribution.
• the ability to perform real-time diagnostics or preventive maintenance operations is crucial to maintaining such a network in an optimal state of operation.
• the visual checks thus carried out make it possible to locate certain malfunctions, and sometimes to determine their causes, or to trigger maintenance actions, when the advanced wear of a part is detected, for example.
• Such controls do not, however, make it possible to inspect the internal characteristics of the network structure or to identify any hidden faults.
• a system monitoring system comprising a structure, such as a network of overhead power lines, for detecting a state or a malfunction of said network of overhead power lines quickly and efficiently.
• the present invention proposes a system for monitoring an assembly having a structure, such as a network of overhead power lines, said system comprising at least one piezoelectric sensor capable of measuring the vibrations of said structure , as well as means for recording a signal representative of said vibrations.
• the system further comprises processing means by means of which the signal is compared by means adapted to one or more known characteristic patterns, to detect a state or a malfunction of the whole, or even to locate precisely a detected malfunction.
• the at least one piezoelectric sensor may be provided, including microphones, accelerometers or gyroscopes.
• microphones including microphones, accelerometers or gyroscopes.
• accelerometers including accelerometers or gyroscopes.
• gyroscopes including accelerometers, gyroscopes.
• the implementation of several piezoelectric sensors to allow vibration analysis of the structure forms to this day the preferred embodiment of the invention.
• the invention relates to a system for detecting a state or a malfunction of an assembly comprising a structure, said system comprising a device for sensing vibrations of the structure, said device for sensing vibrations of the structure comprising at least one piezoelectric sensor in mechanical connection with said structure, said system further comprising means for recording a signal representative of the vibrations of the structure and means for processing said signal to detect a state or a malfunction of the assembly, said processing means comprising means for transforming said signal to form a spectrum representative of the state or dysfunction, the system further comprising means for comparing said spectrum with a plurality of patterns respectively characteristic of a state or a malfunction of the whole, so as to identify the condition or the dysfunction operation of the whole.
• the system according to the invention it is possible to set up remotely and quickly a diagnosis relating to the state or a malfunction of a structure, including an extended structure such as a network of power lines. or a network of railroads.
• the system according to the invention further comprises means for characterizing the state or the malfunction.
• the processing means comprise Fourrier transforming means of said signal to form a spectrum representative of the vibrations of the structure.
• the comparison means perform a statistical comparison.
• the characteristic pattern is a statistical pattern and the comparison means perform a Euclidean distance calculation between the statistical characteristic pattern and the representative spectrum of the vibrations of the structure at a given moment, over a sampling period.
• the comparison means comprise a learning program based on a neural network.
• the system according to the invention comprises at least three piezoelectric sensors of different sensitivity.
• the present invention also provides a method for detecting a state or a malfunction in an overhead power line network, said network comprising a structure comprising at least one tower and at least one overhead electrical cable, said method comprising the implementation of the system briefly. described above, said at least one piezoelectric sensor being mechanically connected to the structure of said network of overhead power lines.
• the fixing of said at least one piezoelectric sensor on said at least one pylon is achieved.
• the present invention also provides a method for predicting a future state or malfunction of a network of overhead power lines, comprising implementing the method for detecting a state or a malfunction in said overhead power line network as briefly described. above, and a step of statistically processing the detected states and / or malfunctions of the overhead power line network to predict a future state or malfunction of said network of overhead power lines.
• Figure 1 illustrates the implementation of a system part according to the invention on a network of overhead power lines.
• FIG. 2 shows a first representative spectrum of the vibrations of a structure, picked up by a system according to the invention.
• FIG. 3 shows a second spectrum representative of the vibrations of a structure, picked up by a system according to the invention.
• FIG. 4 shows a third spectrum representative of the vibrations of a structure, picked up by a system according to the invention.
• FIG. 5 illustrates a method of locating the occurrence of a shock on a network of overhead power lines, by means of a system according to the invention.
• the system according to the invention is applicable to different technical fields, through variant embodiments.
• the invention is mainly described in the context of an implementation for detecting a state or a malfunction of a network of overhead power lines.
• system described below can be adapted to allow the detection of malfunctions in other types of structures, such as the structure of a vehicle, for example an aircraft, or a network of railroads for example.
• FIG. 1 shows a diagram of a portion of a network R of overhead power lines C equipped with a system S for detecting a state or a malfunction of said network R, according to the invention.
• At least one piezoelectric sensor Z of the system S is positioned in mechanical connection with the structure of the network R of overhead electrical lines, namely a part of the pylon P, or alternatively with an electric cable C of the overhead power line.
• said at least one piezoelectric sensor Z is fixed on the pylon P, since this makes it possible to set up a wired connection with a housing comprising processing means.
• the installation of said at least one piezoelectric sensor Z is however possible directly on the cable C.
• said piezoelectric sensor Z is connected to the processing means in a non-wired manner.
• piezoelectric sensor Z can in this case be fixed directly on the cable C, typically by means of an isolated pole, without the current in the overhead power line being cut.
• a piezoelectric sensor Z may be composed of a thin plate of a quartz crystal connected to an operational amplifier.
• three piezoelectric sensors Z are provided. These piezoelectric sensors Z may be identical. Said piezoelectric sensors Z are moreover preferably supplied with different amplification levels relative to one another. In the latter case, their respective different sensitivity makes it possible to optimally capture all the vibrations of the structure, as is detailed in the remainder of this document.
• the recording, by suitable recording means, of a signal representative of the vibrations of the structure detected by means of said at least one piezoelectric sensor Z is provided.
• the recording of the signal is carried out in the form of digital files with a sampling frequency equal to or greater than 2000 Hz.
• This particular sampling frequency for recording the signal representative of the vibrations of the structure, can identify signals up to a frequency of 1 kHz, to detect and identify many states and malfunctions in a network R of overhead power lines.
• Processing means are provided for processing the signal formed by recording the vibrations of the structure detected by means of said at least one piezoelectric sensor Z.
• said processing means comprise means for transforming the signal via a Fourier transform, preferably short period.
• the Fourier transformation is applied to the signal representative of the vibrations of the time slot structure of 1000 samples, corresponding, for a sampling frequency of about 2000 Hz, to a duration of half a second.
• a decomposition of the signal according to the different frequencies that compose it is thus obtained.
• the frequencies whose intensity is constant over the time window considered, corresponding to noise can be filtered in order to keep only the frequencies corresponding to states or non-permanent malfunctions.
• the system according to the invention therefore makes it possible to remotely detect the passage of the current in an overhead power line, and thus, if necessary, to warn technicians to intervene on said line to inform them.
• the system according to the invention allows the detection of the swing of an overhead power line, in particular to trigger preventive maintenance operations.
• the swing of the overhead power lines generates a characteristic spectrum of the signal.
• the present signal of the vibrations of the structure indeed has, because of this sway, a amplitude broad in frequency over a duration of several minutes to several hours.
• a wide range B is observed on the spectrum due to a swing of the overhead power line.
• This characteristic pattern can be detected and analyzed so as to account, by means of suitable calculation means, provided in one embodiment of the system according to the invention, the duration and amplitude of the swings of the overhead power line.
• each supervised overhead electrical line can also be compared with the wear of the eyelets (parts used to suspend the overhead power lines), in order to anticipate their break and to trigger possible operations. preventive maintenance. Indeed, the more the swing of a line is intense, the more the carnations which suspend it will quickly wear out.
• the observation of the sway of a power line in terms of frequency, intensity and duration in particular, allows the estimation, remotely, thanks to means of statistical processing, of the wear of the eyelets that suspend it.
• the analysis of the spectrum obtained by performing, on a predefined sampling window, a Fourier transformation and a filtering of the signal resulting from the recording of the vibrations of the structure detected by the said at least one piezoelectric sensor Z allows to detect the occurrence of shocks on the network R of overhead power lines, and, preferably, their location.
• Figure 4 the spectrum of Figure 4 comprises vertical lines H, substantially at all frequencies shown. These vertical lines, of short duration, correspond to a shock.
• At least three piezoelectric sensors are implemented.
• said three piezoelectric sensors are identical and have, by adjustment, different sensitivities.
• a first piezoelectric sensor with low sensitivity will only activate for strong signal intensities.
• a second piezoelectric sensor, with moderate sensitivity will activate for medium intensities and a third piezoelectric sensor, with strong sensitivity, will activate for all the weakest signals.
• the second piezoelectric sensor with medium sensitivity, can be calibrated so that the presence of a vertical line on the spectrum, obtained from the signal corresponding to the vibrations recorded by means of said second sensor, reflects the rupture of a strand. of the power line.
• each line having a known and finite number of strands the system according to the invention is able to detect all of these vertical lines and counts.
• the lines present only on the spectrum of the piezoelectric sensor with strong sensitivity there are three types of vertical lines: the lines present only on the spectrum of the piezoelectric sensor with strong sensitivity; those present on the spectra of piezoelectric sensors with high and medium sensitivities; finally, the lines present on the spectra of all the piezoelectric sensors.
• the three piezoelectric sensors are calibrated so that the strand breaks are detected on the piezoelectric sensors with high and medium sensitivity.
• the system according to the invention makes it possible to detect breaks in strands and thus to prevent the competent services of the operator of the overhead power line network to trigger a preventive maintenance operation when the number of broken strands becomes critical.
• the system according to the invention also makes it possible to locate detected shocks occurring, for example on a network of overhead power lines R.
• the system S1, S2 according to the invention at two points remote from the structure.
• Each system S1, S2 for detecting a state or a malfunction of the assembly comprising the structure, according to the present invention comprises at least one piezoelectric sensor, means for recording a signal representative of the vibrations of the structure, detected by said at least one piezoelectric sensor, and means for processing these signals.
• each of the systems S1, S2 according to the invention comprises a clock, the clocks of said systems being synchronized. Moreover, the distance D between said two systems S1, S2 is known.
• the systems according to the invention comprise calculation means for determining the distance dx between the midpoint between the two systems S1, S2 and the location of the shock H, according to the following formula: dAt
• At is the time difference measured between the detection of the shock H on the spectrum of one system and the detection of the same shock on the spectrum of the other system, the shock having occurred between said two systems, and dx and Atmax being defined as previously described.
• the invention in order to determine a state or a malfunction of an assembly comprising a structure, such as a network of overhead power lines, to obtain spectra representative of the vibrations of said structure.
• a structure such as a network of overhead power lines
• at least one piezoelectric sensor mechanically connected to the structure in question, detects the vibrations of said structure.
• the vibrations are recorded to form a signal representative of the vibrations of the structure.
• suitable processing means said signal is processed.
• a Fourier transformation and a filtering of the frequencies of constant intensity are provided on a predefined sampling window, typically corresponding to a half-second of recording, to form a spectrum. representative of the vibrations of the structure.
• Means for characterizing the detected state or malfunction of the set comprising the The structure therefore comprises means for comparing the spectra obtained with characteristic patterns corresponding to known spectra representative of a known state or dysfunction.
• said comparison means may comprise a learning program based on a neural network.
• a first type of characteristic pattern thus comprises a vertical line followed by a horizontal line located at a frequency of 0.05 kHz, for detecting the tilting of a line switch and the current flow in said overhead line.
• a second type of characteristic pattern thus comprises a wide frequency amplitude over a period greater than several minutes, typically at least 15 minutes, for measuring the sway of an overhead power line.
• a third type of characteristic pattern thus comprises vertical lines, of short duration, of the order of 100 milliseconds, substantially at all the frequencies shown.
• an automatic and remote diagnosis of the assembly comprising the structure is allowed, based on the vibrations of the structure measured by means of at least one piezoelectric sensor. mechanical connection with said structure.
• the statistical analysis of the detected states and / or dysfunctions of the structure makes it possible to predict a future state, in particular a state of wear, or else a future malfunction of the assembly. Therefore, the planning of preventive maintenance operations can be optimized by the present invention.
• breaks in strands are detected, said breaks are counted and, beyond a certain threshold, it may be provided to make a cable change because the risk of total rupture of said cable becomes high compared to the number of broken strands.
• the eyelet wear level can be estimated according to a detection of the swing of the cable, said detection being obtained in particular by means of the implementation of a neural network, so as to allow a preventive maintenance of the eyelets before breaking.
• the "life expectancy" of the assembly comprising the structure can be estimated by means of the present invention.
• a railroad network or the structure of an aircraft allow the implementation of the invention to determine a state or a malfunction, respectively of the railways or the aircraft concerned.
• the number and sensitivity of the piezoelectric sensors can be adapted.
• the characteristic patterns are also suitably determined.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Aviation & Aerospace Engineering (AREA)
• Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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• 2017
  • 2017-04-24 FR FR1753518A patent/FR3065526B1/fr active Active
• 2018
  • 2018-04-23 EP EP18724145.0A patent/EP3615906A1/de not_active Withdrawn
  • 2018-04-23 WO PCT/EP2018/060390 patent/WO2018197440A1/fr unknown

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