Device and method for determining the mechanical tension of a catenary contact wire

Abstract

The invention relates to a device (1) for determining an actual tension (tr) of a contact wire (c) of a catenary extending above a railway track, the device comprising: - means for suspending (4) the device (1) on the contact wire (c); - an application element (5) of a bending force capable of causing the contact wire (c) located between the two stops (40) to take an angle, the application element (5) of a bending force comprising an electric motor (51); - a force sensor (60); - measuring means; - an electronic system (7) capable of determining a calculated stiffness (rc), and the actual mechanical tension of the contact wire (c).

Description

[0001] The field of the invention is that of the design and manufacture of maintenance equipment for railway installations.

[0002] More specifically, the invention relates to a device for maintaining equipment for supplying electrical current to train locomotives operating on a railway track.

[0003] In the field of the invention, it is known to transmit electric current to the train traveling on a railway track by means of at least one contact wire above the railway track.

[0004] Such a contact wire supplies current to pantographs located on the upper part of a locomotive. The pantograph is a device that allows a locomotive to collect current by friction against the contact wire of a catenary.

[0005] One or more contact wires may be suspended from a main cable by means of a series of vertical cables called droppers, the lengths of which are adapted to keep the contact wire approximately horizontal. The assembly formed by the contact wire, the droppers, and the main cable is conventionally referred to as a "catenary" or an "overhead contact line."

[0006] Such a catenary is supported above the railway by support poles placed at intervals along the railway.

[0007] A catenary contact wire is classically presented in the form of a longitudinal element, preferably equipped with two lateral and longitudinal fixing grooves to allow, in particular, the connection of the contact wire with the catenary pendulums or an auxiliary carrier cable.

[0008] Naturally, as trains pass, the pantographs of the locomotives rub against the underside of the contact wires, causing wear. In practice, this wear results in a flat spot forming on the underside of the contact wire, reducing its thickness.

[0009] The characteristics of a contact wire thus evolve with time and wear, and it is important to check them periodically, in order to ensure the proper functioning of the contact wire or to schedule an appropriate maintenance operation.

[0010] The mechanical tension of the contact wire is also an important characteristic for ensuring the condition of a railway network.

[0011] No equipment is known that is particularly suitable for carrying out such a mechanical tension measurement on the contact wire of a catenary of a railway track, this contact wire being located several meters above ground level.

[0012] However, mechanical stop tensiometers are known to allow this mechanical tension to be determined.

[0013] These mechanical stop tensiometers include a frame in the shape of a T.

[0014] The building thus presents: a central part; two arms extending from an upper end of the central part, and on either side of this central part.

[0015] This frame is designed to be suspended from a catenary contact wire. Each arm has fixed stops beneath which the contact wire can be inserted and made contact with the stops to suspend the frame.

[0016] On the central part of the frame, a support head is designed to make contact with the contact wire to angle it. This support head is movable along a translational axis located between the two fixed stops, and is designed to be perpendicular to a section of the contact wire extending between the stops.

[0017] This support head is mounted at the end of a screw that is operated by a handwheel. The handwheel allows the support head to be moved so that it presses against the contact wire.

[0018] The central part also features a central stop, opposite the support head. The support head is designed to press the contact wire until it makes contact with the central stop. Following full rotation of the clamping handwheel, the contact wire is thus positioned at a predetermined angle.

[0019] Each of the frame arms carries a strain gauge which allows the force to be measured when the force is applied to the contact wire, once the contact wire has taken the predetermined angle.

[0020] This solution, which can be used in the field, requires the use of a platform to bring the operator performing the check to the height of the contact wire.

[0021] The mechanical stop tensiometer also has the disadvantage that it tends to cause permanent deformation of the contact wire, very often observed after measurement.

[0022] Furthermore, the measurement process involves imposing a predetermined angle through the use of stops. Consequently, if the wire is not straight or has dents, then the overall geometry is not perfect and the final measurement is less precise.

[0023] The tool itself is not perfectly precise. This necessitates taking multiple measurements on different parts of the contact wire to improve the accuracy of the final result.

[0024] The tool must also be turned over to take a second measurement on each point and, despite this, an inaccuracy persists and the dispersion of measurements is ultimately unacceptable.

[0025] It is important to note that voltage measurements using such a tool are inaccurate if the contact wire is worn. It is indeed difficult to account for this factor and obtain a reliable result.

[0026] Finally, it can be noted that the operation of applying pressure using this tool is tedious, as the clamping handwheel must be operated manually by the user.

[0027] Document WO99 / 67612 A2 discloses a device for determining the actual mechanical tension of a catenary contact wire according to the prior art.

[0028] The invention aims in particular to overcome the drawbacks of the prior art.

[0029] More specifically, the invention aims to provide a device that allows the actual mechanical tension of a catenary contact wire to be determined.

[0030] The invention also aims to provide such a device which allows the actual mechanical tension to be obtained in a simple and safe manner for the operator using the device, and more particularly a device which allows a measurement of the mechanical tension to be made from the ground, without the use of a lifting device.

[0031] The invention further aims to provide such a device which allows a determination of a real mechanical tension particularly precise without causing permanent deformation of the contact wire after measurement.

[0032] These objectives, as well as others that will appear subsequently, are achieved through the invention, which relates to a device for determining the actual mechanical tension of a contact wire of a catenary extending above a railway track, the device comprising: means for suspending the device on the contact wire, the suspension means comprising two stops, a first fixed stop and a second fixed stop intended to rest on the contact wire; a member for applying a bending force comprising a support head movable along an axis of translation located between the two stops and intended to be perpendicular to a section of the contact wire extending between the two stops, the support head being capable of causing the contact wire located between the two stops to take an angle; characterized in that the element applying a bending force comprises an electric motor driving the support head in motion, the device comprising: a force sensor measuring forces applied by the support head; means for measuring the position of the support head along the axis of translation; and in that it includes an electronic system comprising: means for controlling the electric motor configured to drive the support head to at least two distinct positions corresponding to two different applied forces in which the contact wire takes an angle; first means for calculating a calculated stiffness of the contact wire from a difference between the two distinct positions; second means for calculating the actual mechanical tension of the contact wire from the calculated stiffness and a function for converting a stiffness into a mechanical tension.

[0033] Thanks to the device for determining a real mechanical tension according to the invention, an operator has a powerful tool allowing him to obtain this real tension while benefiting from comfortable measurement conditions.

[0034] Moreover, the actual tension determined proves to be particularly accurate.

[0035] Indeed, thanks to the principle of the invention, the tension of the contact wire is determined by applying a bending force on three points using the device which is powered by an electric motor.

[0036] Such a determination proves practical for the user who does not have to perform a tedious action to determine the mechanical tension of the contact wire.

[0037] Furthermore, the mechanical tension of the contact wire is determined by applying a bending force at three points. During bending, the device measures the displacements generated as a function of the applied radial forces.

[0038] The device's electronic system has the particularity of driving the support head to at least two distinct positions that correspond to two different applied forces.

[0039] The measured displacement between the two positions (resulting from the application of two different forces) allows the first calculation method to determine the actual calculated stiffness of the contact wire. Subsequently, the second calculation method allows the actual mechanical tension to be obtained using the calculated stiffness via at least one conversion function, which is, of course, pre-programmed into the electronic system of the determination device according to the invention.

[0040] This method offers the advantage of allowing the determination of actual mechanical tension for the contact wires. Indeed, if the contact wire is worn, its wear can be determined by the device by measuring its thickness and incorporating this measurement into the calculation performed by the secondary calculation methods. As detailed below, this wear level can be determined using the support head and the force sensor.

[0041] According to a preferred embodiment, the device comprises a pole and a frame supported by the pole, the frame having the suspension means, the element for applying a bending force, the force sensor, and the measurement means.

[0042] Determining the actual mechanical tension of the contact wire using the device according to the invention is thus particularly simple to be carried out by an operator.

[0043] Indeed, this operator simply needs to position themselves under the contact wire to suspend the frame from the railway track. This operator then does not need to use a lifting device to reach the same level as the contact wire.

[0044] In this case, the electronic system advantageously includes a mobile electronic unit with a screen, the electronic unit communicating wirelessly with the frame.

[0045] Thanks to this electronic unit, the operator can easily obtain the information sought, including the actual mechanical tension which can be displayed on the screen from the ground.

[0046] Thus, he does not have to remove the suspended frame from the contact wire to read information that would be located on the frame itself.

[0047] Advantageously, the device includes means for coupling and decoupling the frame with the pole, the frame including an electric battery.

[0048] This design allows the pole to be disassembled from the frame when the latter is suspended from the contact wire.

[0049] The operation of the device and more particularly the determination of the actual mechanical tension of the contact wire is therefore not impacted by the weight of the pole, nor by any action that the operator could perform on the pole during the measurement and which would impact the way in which the frame operates to obtain the measurements.

[0050] Also, thanks to this design, the frame can operate autonomously by being suspended on a contact wire.

[0051] According to an advantageous design, the coupling and decoupling means include a coupling confirmation actuator, the actuator being coupled to the electronic system and the electric motor control means also being configured to exert a holding force on the frame in a suspended position in the absence of actuator activation.

[0052] This design allows the frame to be secured on the contact wire in the absence of coupling of the frame with the pole.

[0053] Indeed, when an operator detaches the pole from the frame after suspending the latter, the frame cannot fall. It is only when the pole is reattached to the frame that the electronic system and control mechanisms cease to exert a force to maintain the frame in the suspended position on the contact wire.

[0054] According to a preferred embodiment, the electronic system is programmed with a plurality of functions for converting a stiffness into a mechanical tension, each conversion function being specific to a type of contact wire and / or a wear state of the contact wire, the electronic system including means for selecting one of the conversion functions to be implemented by the second calculation means.

[0055] Thanks to this embodiment, the device for determining a real mechanical tension according to the invention can be used on different types of contact wires (for example contact wires of different sizes), thus allowing great versatility of use for the device.

[0056] Furthermore, the wear level can then specifically contribute to the selection of the most suitable conversion function. Proper integration of the wear level is important because it has been observed that wear can have a significant impact on the calculation of the actual mechanical stress.

[0057] In this case, and according to a first solution, the conversion function(s) take the form Y = aX + b, where: The parameter Y is the calculated stiffness; the parameter X is the actual mechanical tension; the parameter a is a slope coefficient; the parameter b is the y-intercept.

[0058] Various series of measurements on contact wires in several states (new, medium, and worn) have revealed relationships between the measured values ​​and the actual mechanical stresses that exhibit near-perfect linearity. The experimental determination of one or more conversion functions in the form of affine functions thus allows for a particularly precise determination of the actual mechanical stress of the contact wire, while also facilitating the implementation of the determination method using the device.

[0059] According to another solution, the conversion function or functions take the form of a lookup table between a stiffness and a mechanical tension.

[0060] Such a solution forms an even more accurate model than the one previously described, but requires very large memory resources for the electronic system.

[0061] According to a preferred feature, the device has two guide lugs extending laterally at an angle from the stops, the guide lugs forming hooks suitable for hooking the contact wire.

[0062] These guide tabs facilitate the suspension of the device on the contact wire. They guide the contact wire to the stops of the suspension means.

[0063] Furthermore, these guide legs prove particularly useful for an operator when the device is equipped with a pole for supporting the frame. Indeed, from the ground, an operator can then more easily suspend the device on the contact wire thanks to the guidance provided by the two guide legs.

[0064] Advantageously, the device includes a contact wire temperature sensor, with correlation means incorporating a temperature measurement to obtain an actual voltage. More precisely, it is an infrared temperature sensor directed at the contact wire, measuring its temperature directly.

[0065] When measuring an uncompensated catenary cross-section, the contact wire hangs between two fixed points, and the mechanical tension of the cable is temperature-dependent. On an uncompensated catenary, and for a specific type of installation (wire type, wire cross-section, distance between fixed points), a given reference temperature corresponds to a specific mechanical tension.

[0066] Thanks to voltage measurement and direct temperature measurement, it is then possible to indicate the measured voltage and the voltage correlated with the temperature.

[0067] The invention also relates to a method for determining the mechanical tension of a contact wire of a catenary extending above a railway track, the method comprising: a first step of applying a bending force on a portion of the contact wire to a first predefined force (F1); a first step of measuring a first radial displacement (D1) of the portion of the contact wire generated during the first application step; a second step of applying a bending force on the portion of the contact wire to a second predefined force (F2); a second step of measuring a second radial displacement (D2) of the portion of the contact wire generated during the second application step; a first calculation step to determine a calculated stiffness of the contact wire from a calculated difference between the second radial displacement (D2) and the first radial displacement (D1), the first force (F1) and the second force (F2); a second calculation step to determine the actual mechanical tension from the calculated stiffness and a conversion function.

[0068] The determination method according to the invention has the ability to precisely determine the mechanical tension of a contact wire of a catenary.

[0069] The first step in applying a bending force to a portion of the contact wire is performed at three points. More precisely, a bending force is applied at a central point located between two fixed points. The resulting radial displacement allows for the precise determination of the mechanical tension via the calculated stiffness, without causing any deformation of the contact wire.

[0070] Advantageously, the process includes a preliminary step of measuring the thickness of the contact wire, and a step of selecting the conversion function, from among a plurality of conversion functions, to be implemented in the second calculation step as a function of a thickness of the contact wire.

[0071] Thus, the process makes it possible to determine the mechanical tension of a worn contact wire.

[0072] Other features and advantages of the invention will become more apparent upon reading the following description of a preferred embodiment of the invention, given by way of illustrative and non-limiting example, and the accompanying drawings, among which: there figure 1 is a schematic representation of the determination device according to the invention, the device comprising a frame, a pole supporting the frame, and an electronic system comprising a movable electronic unit; the figure 2 is a perspective view of the frame of the determination device according to the invention; the figure 3 is a perspective representation of the structure suspended on a catenary contact wire, an electronic control unit visible on the figure 2 being removed from the structure; the figure 4 is a schematic representation based on a cross-section of the frame of the figure 3 ; there figure 5 is a schematic representation of the suspension of the frame on a contact wire of a catenary; the figure 6 illustrates the method of determining a voltage according to the invention.

[0073] With reference to the figure 1 , a device 1 for determining an actual mechanical tension TR of a contact wire C of a catenary is shown.

[0074] Device 1 includes: a pole 3; a frame 2 which includes, as detailed later, a chassis 21 and an electronic control block 22; an electronic system 7 which includes a mobile electronic unit 8, corresponding for example to a smartphone.

[0075] Pole 3 allows frame 2 to be lifted from the ground.

[0076] With reference to figures 1 à 4 Device 1 comprises: means for suspending 4 of the device 1 on the contact wire C; an application element 5 of a bending force; a force sensor 60; measuring means.

[0077] The means of suspension 4, the element of application 5 of a bending force, the force sensor 60 and the measuring means are, according to the present embodiment, represented by the frame 2.

[0078] The means of suspending device 4 on the contact wire C thus allow the frame 2 to be suspended on the contact wire C.

[0079] These suspension means 4 include two stops 40. More particularly, these suspension means 4 include a first fixed stop 41 and a second fixed stop 42, both of which are intended to rest on the contact wire C.

[0080] The stops 40 are in particular fixed rollers which, as described in more detail later, allow for and provide flexural support for the contact wire C. The stops 40 each have a groove allowing the contact wire C to be centered when positioned on it.

[0081] The application element 5 of a bending force includes a support head 50 which is movable along a translation axis T.

[0082] The translation axis T is located between the two stops 40. In other words, this translation axis T is equidistant from the stops 40. The translation axis T is intended to be essentially perpendicular to a section of the contact wire C which extends between the two stops 40, and this when the contact wire C extends in an essentially straight line between the stops 40.

[0083] This support head 50 is likely to cause the contact wire C located between the two stops 40 to take an angle.

[0084] The application element 5 of a bending force also includes linear guide bearings 52 which ensure proper translation along the translation axis T of the support head 50.

[0085] The force sensor 60 allows the measurement of forces applied by the support head 50. This force sensor 60 is thus intended to measure a force applied by the support head 50 on the contact wire C.

[0086] Finally, the measuring means allow the position of the support head 50 to be measured along the translation axis T.

[0087] In other words, the measuring means allow the position of the support head 50 to be determined, and the force sensor 60 allows the force applied by the support head 50 to be determined at a given position.

[0088] According to the principle of the invention, the application member 5 of a bending force comprises an electric motor 51 which drives the support head 50 in mobility.

[0089] This electric motor 51 notably takes the form of an electric actuator.

[0090] The electric actuator is equipped with a quadratic encoder which provides the means of measurement. Indeed, the quadratic encoder allows the direction and value of the displacement of the support head 50 to be determined.

[0091] With reference to the figure 3 The device also includes a temperature sensor 62 for the contact wire C. More precisely, it is an infrared temperature sensor oriented directly towards the contact wire C to measure its temperature.

[0092] The temperature sensor 63 is supported by the frame 2.

[0093] As mentioned previously, and still with reference to figures 1 And 2, device 1 includes an electronic system 7.

[0094] This electronic system 7 is programmed with at least one function for converting P1, P2, P3 from a stiffness into a mechanical tension.

[0095] In this case, the electronic system 7 is programmed with three conversion functions P1, P2, P3 and these conversion functions P1, P2, P3 are integrated into a memory 75 of the electronic system 7.

[0096] With reference to the figure 1 The electronic system 7 includes: control means 70 of the electric motor 51; first means of calculation 71 of a calculated stiffness RC of the contact wire C; second means of calculation 72 of the actual mechanical tension TR of the contact wire C from the calculated stiffness RC and one of the conversion functions P1, P2, P3 of a stiffness into a mechanical tension.

[0097] The control means 70 of the electric motor 51 are integrated into the electronic control block 21.

[0098] The control means 70 allow the support head 50 to be driven, using the electric motor 51, to at least two distinct positions corresponding to two different applied forces in which the contact wire C takes an angle.

[0099] The angle formed by the contact wire C is therefore not predefined, and it is according to its actual characteristics that the angles which it takes under the effect of the support head are more or less pronounced.

[0100] The first means of calculation 71 of the calculated stiffness RC of the contact wire C perform the calculation from a difference in displacement of the support head 50 (and thus of the contact wire C) between the two positions reached by the support head 50 (or in other words the two angles taken by the contact wire) during the application of each of the two different applied forces.

[0101] More specifically, and as further developed, the first means of calculation use the force applied by the support head 50 and measured by the force sensor 60 at each of the distinct positions.

[0102] According to the present embodiment, the second calculation means 72 incorporate a temperature measurement to obtain the actual mechanical tension TR. This temperature measurement is obtained by the temperature sensor 62 of the contact wire C.

[0103] As illustrated by the figure 1 and according to the present embodiment, the electronic system 7 is split into two parts, the first part of which is embedded in the electronic control block 21 of the frame 2 and the other part of which is embedded in the electronic unit 8.

[0104] According to other possible embodiments, the entire electronic system 7 can be integrated into the frame 2.

[0105] With reference to the figure 1 and in the present embodiment, the electronic system 7 includes wireless communication means 73.

[0106] These wireless communication means 73 are specifically configured to operate via Bluetooth (registered trademark) and allow bidirectional communication between frame 2 and electronic unit 8.

[0107] The electronic unit 8 includes the first computing means 71, the second computing means 72 and the memory 75.

[0108] The electronic system 7 further includes selection means 74, presented by the electronic unit 8. These selection means 74 allow one of the conversion functions P1, P2, P3 to be selected to be implemented by the second calculation means 72.

[0109] The use of a plurality of conversion functions P1, P2, P3, allows to have conversion functions which are specific to a single type of contact wire C.

[0110] The selection means 74 may include a selection interface for indicating the type of contact wire C on which the device is used to select a suitable conversion function.

[0111] Thus, depending on the calibers of the contact wires C analyzed, the appropriate conversion function can be selected via the selection interface.

[0112] The mobile electronic unit 8 has a screen 80. This screen 80 allows information to be displayed and selected from the electronic unit 8.

[0113] In this instance, and as illustrated by the figure 1 , the screen 80 of the electronic unit 8 allows the selection interface of the selection means 74 to be displayed, then the actual voltage TR obtained by the second calculation means 72 to be displayed.

[0114] The frame 2 thus comprises the chassis 21 and the electronic control unit 22.

[0115] According to the present embodiment, the electronic control unit 22 also incorporates an electric battery 20.

[0116] With reference to the figure 2 The electronic control unit 22 is equipped with: of an on / off switch 221; of a charging socket 222 for the electric battery 20; of a status indicator 223 allowing an operator to have visual feedback on the status (device on, in operation or faulty).

[0117] The 20 electric battery allows the frame 2 to be autonomous.

[0118] Device 1 includes coupling and decoupling means 30 of the frame 2 with the pole 3. These coupling and decoupling means 30 allow the pole 3 to be disassembled from the frame 2 when the latter is suspended on the contact wire C.

[0119] More specifically, and as illustrated by the figures 1 à 4 , the coupling and decoupling means 30 include a magnetic cone 300 presented by the frame 2, and a funnel 301 complementary to the magnetic cone 300, the funnel 301 being presented by the pole 3.

[0120] The coupling and decoupling means 30 further include a coupling confirmation actuator (not shown). This actuator is coupled to the electronic system 7, and the control means 70 of the electric motor 51 are configured to exert a holding force on the frame 2 in a suspended position in the absence of actuator activation.

[0121] After suspending the frame 2 on the contact wire C using the pole 3, decoupling the pole 3 by means of the coupling and decoupling means 30 causes a change in the state of the actuator, which, by means of the electronic system 7, allows the control means 70 to exert a holding force on the frame 2 on the contact wire C.

[0122] This holding effort simply corresponds to a movement of the support head 50 to hold the contact wire C captive. Such a situation is represented on the figure 5 .

[0123] If an operator recouples the pole 3 to the frame 2, then the coupling confirmation actuator has its state changed and the control means 70 then cease to exert a force to maintain the frame 2 in a suspended position on the contact wire C.

[0124] It is thus understood that the electric battery 20 of the frame 2 allows the frame 2 to act autonomously with respect to the energy supply following the decoupling of the pole 3 of the frame 2.

[0125] With reference to figures 1 à 4 , as well as to the figure 5 The device 1 comprises two guide lugs 9 which extend laterally at an angle from the stops 40. These guide lugs 9 form hooks suitable for hooking the contact wire C as illustrated by the figure 5 .

[0126] With reference to the figure 5 The installation of device 1 on a contact wire C is described below.

[0127] The first three steps (described below) of setting up the frame 2 on the contact wire C are carried out using a pole 3.

[0128] Of course, the frame 2 can be manually positioned on the contact wire C, according to another embodiment, in which the operator must manipulate it directly. In this case, the operator needs a lifting device to reach the contact wire C.

[0129] To set up device 1, the operator must position the frame 2 so that it is opposite an opening located directly below the two guide legs 9 which extend laterally at an angle from the stops 40. The opening is more precisely located between the guide legs 9 which form hooks, and the support head 50.

[0130] Device 1 is then moved so as to engage the contact wire C under the guide tabs 9.

[0131] Device 1 is further moved to position contact wire C under stops 40, and more precisely inside the grooves presented by each of stops 40.

[0132] In this situation, the frame 2 is suspended on the contact wire C. The operator can then detach the pole 3 from the frame 2. The coupling confirmation actuator 30 ceases to be activated. This directly causes the support head 50 to rise under the effect of the control means 70 of the electric motor 51, exerting a force to hold the frame 2 in the suspended position.

[0133] It is understood that in order to remove device 1 from contact wire C, an operator must perform the operation in the reverse direction of that of the elements described.

[0134] With reference to figures 1 And 6The method for determining the actual voltage TR of a contact wire C of a catenary is described. This determination method is implemented by the device 1 according to the invention described above.

[0135] The process includes a first step of applying a bending force E1 to a portion of the contact wire C to a first predefined force F1.

[0136] The first predefined force F1 is non-zero. By this first application step E1, the contact wire C takes an angle which is a function of the characteristics of the contact wire C and the first predefined force F1.

[0137] The first step E1 is followed by a first measurement step M1 of a first radial displacement D1 of the portion of the contact wire C generated during the first application step E1.

[0138] The first radial displacement D1 corresponds in particular to the distance of displacement of the support head 50 between the position in which the support head 50 is in contact with the contact wire C and / or this contact wire C does not take an angle under the effect of the device 1.

[0139] The first radial displacement D1 is recorded.

[0140] The process then similarly includes a second step of applying a bending force E2 to the portion of the contact wire C to a second predefined force F2.

[0141] The second predefined force F2 is non-zero and advantageously greater than the first predefined force F1.

[0142] As an example, the first force F1 can be equivalent to 10 daN and the second force F2 can be equivalent to 70 daN.

[0143] This second application step E2 is followed by the second measurement step M2 of a second radial displacement D2 of the portion of the contact wire C generated during the second application step E2.

[0144] This measurement step M2 of a second radial displacement D2 allows the recording of the measurement of the second radial displacement D2.

[0145] Following these steps, the process includes a first calculation step CAL1 to determine a calculated stiffness RC of the contact wire C from: of a calculated difference between the second radial displacement D2 and the first radial displacement D1; of the first force F1; of the second force F2.

[0146] The calculation performed is as follows: RC = (F2 - F1) / (D2 - D1).

[0147] This first calculation step CAL1 is implemented by the first calculation means 71.

[0148] The process finally includes a second calculation step CAL2 to determine the actual tension TR of the contact wire C from the calculated stiffness RC and a conversion function P1, P2, P3...

[0149] This second calculation step CAL2 is implemented by the second calculation means 72.

[0150] According to the present embodiment, the conversion functions P1, P2, P3 take the form Y = aX + b, where: the parameter Y is the calculated stiffness RC; the parameter X is the actual mechanical tension TR; the parameter a is a slope coefficient; the parameter b is the ordinate at the origin.

[0151] Various series of measurements of mechanical tension and stiffness on contact wires have revealed that the curve representing the evolution of mechanical tension as a function of stiffness exhibits almost perfect linearity. A straight line can be obtained using a least-squares method, which allows for the determination of the specific parameters a and b for a given contact wire.

[0152] The calculation performed to obtain the actual mechanical tension is as follows: Actual tension TR = (Calculated stiffness RC - b) / a

[0153] This gives the actual voltage TR of the contact wire C.

[0154] According to another conceivable embodiment, the conversion function or functions P1, P2, P3 take the form of a correspondence table between a stiffness and a mechanical tension.

[0155] Such a correspondence table can be useful in the case where the behavior of the mechanical tension of the contact wire C with respect to its stiffness would not be transposable to that of a determinable mathematical function.

[0156] The device according to the invention also makes it possible to estimate the wear of the contact wire C.

[0157] The process thus includes a preliminary step of measuring the thickness of the contact wire C, and the second calculation step CAL2 integrates the measurement of the thickness of the contact wire C for the determination of the actual voltage TR.

[0158] To this end, it has been noted that the wear of the contact wire C influences the evolution curve of the mechanical tension as a function of the stiffness, but that for a given wear an almost perfect linearity can always be observed.

[0159] Thus, for a type of contact wire C, several conversion functions P1, P2, P3 are determined for different wear states of the contact wire C.

[0160] These conversion functions each take the form Y = aX + b, and correspond for example to a new state P1, to a wear of 50% P2, and to a wear of 100% P3.

[0161] The device according to the invention thus makes it possible to determine this level of wear in the manner described below.

[0162] When the device is suspended on the contact wire C, the contact wire extends substantially in a straight line between the two stops 40.

[0163] It is important to note that at this moment, the wear face of the contact wire, the flat, is located below the contact wire C.

[0164] In this way, it is possible, using the device, to determine: the thickness of the contact wire C; the level of wear of the contact wire C.

[0165] The level of wear can be obtained by comparing the position of the support head 50 when it comes directly into contact with the contact wire C, without applying pressure, to the position that the support head 50 should reach if the contact wire was new.

[0166] To integrate this wear level obtained into the second calculation step CAL2. The process also includes, after the preliminary step of measuring the thickness of the contact wire C, a step of selecting one of the conversion functions P1, P2, P3, from the plurality of conversion functions P1, P2, P3, to be implemented in the second calculation step CAL2 as a function of the thickness of the contact wire C.

[0167] This step of selecting one of the conversion functions P1, P2, P3 is implemented by the selection means 74.

[0168] Device 1 can also be used for a contact wire C which would be a multi-strand cable.

[0169] A multi-strand cable is composed of a number of twisted wires. When the multi-strand cable is subjected to pressure by the support head 50, the arms undergo minute displacements relative to each other. These displacements could potentially distort a stiffness measurement and therefore the calculation of the cable's mechanical tension.

[0170] To minimize error, the method according to the invention may include: a preliminary step, in which a maximum stress is applied to the contact wire C; a reduction of the stress to the prestress value corresponding to the first application step E1; the start of the cycle described above.

[0171] It is important to note that the stress is then never released on the contact wire C during the cycle.

[0172] The measurement cycle is also repeated several times without releasing the constraint.

[0173] An average is then calculated in addition during the first calculation step CAL1, of course without taking into account the first stress which was used to place the strands relative to each other.

Claims

1. A device (1) for determining an actual mechanical tension (TR) of a contact wire (C) of an overhead line extending above a railway track, the device comprising: - means (4) for suspending the device (1) on the contact wire (C), the suspension means (4) comprising two stops (40) including a first fixed stop (41) and a second fixed stop (42) intended to rest on the contact wire (C); - a member (5) for applying a bending load comprising a bearing head (50) movable along an axis of translation (T) located between the two stops (40) and intended to be perpendicular to a section of the contact wire (C) extending between the two stops (40), the bearing head (50) being prone to impart an angle to the contact wire (C) located between the two stops (40); characterised in that the member (5) for applying a bending load comprises an electric motor (51) movably driving the bearing head (50), the device (1) comprising: - a force sensor (60) measuring forces applied by the bearing head (50); - means for measuring a position of the bearing head (50) along the axis of translation (T); and in that it comprises an electronic system (7) comprising: - means (70) for controlling the electric motor (51) configured to drive the bearing head (50) to at least two distinct positions corresponding to two different applied forces in which the contact wire (C) takes an angle; - first means (71) for computing a computed stiffness (RC) of the contact wire (C) from a difference between the two distinct positions; - second means (72) for computing the actual mechanical tension (TR) of the contact wire (C) from the computed stiffness (RC) and from a function (P1, P2, P3) for converting a stiffness into a mechanical tension.

2. The device (1) according to the preceding claim, characterised in that it comprises a pole (3) and a frame (2) carried by the pole (3), the frame (2) having the suspension means (4), the member (5) for applying a bending load, the force sensor (60), and the measuring means.

3. The device (1) according to the preceding claim, characterised in that the electronic system (7) comprises a mobile electronic unit (8) having a screen (80), the electronic unit (8) wirelessly communicating with the frame (2).

4. The device (1) according to any one of claims 2 and 3, characterised in that it comprises means (30) for coupling and decoupling the frame (2) with the pole (3), the frame (2) comprising an electric battery (20).

5. The device (1) according to the preceding claim, characterised in that the coupling and decoupling means (30) comprise an actuator for confirming a coupling, the actuator being coupled to the electronic system (7) and the control means (70) of the electric motor (51) being also configured to exert a load for holding the frame (2) in a suspended position in the absence of an activation of the actuator.

6. The device (1) according to any one of the preceding claims, characterised in that the electronic system (7) is programmed with a plurality of functions (P1, P2, P3) for converting a stiffness into a mechanical tension, each conversion function (P1, P2, P3) being specific to a contact wire (C) type and / or to a wear condition of the contact wire (C), the electronic system (7) comprising means (74) for selecting that one amongst the conversion function (P1, P2, P3) to be implemented by the second computing means (72).

7. The device (1) according to any one of the preceding claims, characterised in that the conversion function(s) (P1, P2, P3) are in the form Y=a.X+b, where: - parameter Y is the computed stiffness (RC); - parameter X is the actual mechanical tension (TR); - parameter a is a slope coefficient; - parameter b is the vertical intercept.

8. The device (1) according to any one of claims 1 to 6, characterised in that the or each conversion function (P1, P2, P3) is in the form of a table of correspondence between a stiffness and a mechanical tension.

9. The device (1) according to any one of the preceding claims, characterised in that it has two guide legs (9) extending laterally obliquely from the stops (40), the guide legs (9) forming hooks adapted to enable hooking of the contact wire (C).

10. The device (1) according to any one of the preceding claims, characterised in that it comprises a sensor (62) for the temperature of the contact wire (C), the second computing means (72) integrating a temperature measurement to obtain the actual mechanical tension (TR).

11. A method for determining an actual mechanical tension (TR) of a contact wire (C) of an overhead line extending above a railway track, the method comprising: - a first step (E1) of applying a bending load on a portion of the contact wire at a predefined first force (F1) ; - a first step (M1) of measuring a first radial displacement (D1) of the portion of the contact wire imparted during the first application step; - a second step (E2) of applying a bending load on the portion of the contact wire at a predefined second force (F2) ; - a second step (M2) of measuring a second radial displacement (D2) of the portion of the contact wire imparted during the second application step; - a first computation step (CAL1) to determine a computed stiffness (RC) of the contact wire from a computed difference between the second radial displacement (D2) and the first radial displacement (D1), from the first force (F1) and from the second force (F2); - a second computation step (CAL2) to determine the actual mechanical tension (TR) from the computed stiffness (RC) and from a conversion function (P1, P2, P3) .

12. The method according to the preceding claim, characterised in that it comprises a prior step of measuring the thickness of the contact wire (C), and a step of selecting the conversion function (P1, P2, P3), amongst a plurality of conversion functions (P1, P2, P3), to be implemented in the second computation step (CAL2) according to the thickness of the contact wire (C).