System for measuring the intensity of an electric current in an electrical cable and associated measurement method

Abstract

A measurement system (1) for the intensity of an electric current flowing in an electric cable to be tested (CT), the measurement system (1) comprising: a support member (2) extending, in a transverse plane (J, K), over an angular range less than or equal to 180° around the cable to be tested (CT); at least three measuring devices (31, 32, 33) mounted on the support member (2), each measuring device (3i) having its own angular position and being configured to measure an ortho-radial component of the magnetic field emitted by the cable to be tested (CT), the ortho-radial component having an amplitude defined according to the formula Si(θi) = C + A1 cos (θi + δθ1) + εi; and a calculator (4) configured to determine the first parameter (C) and the intensity value (I) of the electric current flowing through the cable under test (CT) from the current equation: I = Q / C. Figure 3

Description

Title of the invention: System for measuring the intensity of an electric current in an electrical cable and associated measurement method. Technical field

[0001] The present invention relates to the field of measuring the intensity of an electric current flowing in an electric cable. The invention is particularly applicable to measuring the intensity of an electric current in a catenary of a railway track.

[0002] It is known to measure the intensity of an electric current flowing through an electrical cable to ensure its proper functioning. For this purpose, so-called "non-contact" measurement systems are known, which use magnetic field sensors, for example, Hall effect sensors. To determine a reliable electric current intensity value, such a measurement system generally comprises a plurality of sensors distributed around the cable to be tested.

[0003] However, such measuring systems, which need to extend around the cable being tested, cannot be mounted, for example, on cables positioned near a wall that prevents the sensors from being positioned. Similarly, overhead lines known as "catenary" and intended to supply electricity to a railway vehicle must, for this purpose, be connected to a pantograph mounted on the railway vehicle. The measuring system cannot then extend under the cable being tested.

[0004] In the prior art, measurement systems are also known that extend only partially around the cable to be tested, for example, opposite one half of the cable. However, such systems generally use a signal generator or magnetic coils, or require the addition of a motor, which makes them complex to implement and gives them significant mass and bulk. This presents a significant drawback, particularly for measuring the electric current flowing through a railway catenary suspended between two poles.

[0005] Furthermore, it is sometimes necessary to measure the electric current intensity in a cable under test when one or more other electrical cables are located around it, which can interfere with the measurement. The current measurement is then unreliable.

[0006] The invention thus aims to eliminate at least some of these drawbacks by providing a reliable and compact system for measuring the intensity of an electric current flowing in an electrical cable. The invention relates in particular to a measurement system that can be used on a railway catenary by allowing the passage of a pantograph while ensuring an accurate measurement even in the presence of a disruptive electrical cable nearby. PRESENTATION OF THE INVENTION

[0007] The invention relates to a system for measuring the intensity of an electric current circulating in an electrical cable to be tested, hereinafter referred to as the cable to be tested, the measurement system comprising: a support member comprising a groove extending longitudinally along a principal axis and configured to allow passage of the cable to be tested, the support member defining a plane transverse to the principal axis which includes a test area, the support member extending, in the transverse plane, over an angular range around the test area less than or equal to 180°, the cable to be tested being configured to extend into the test area when in use, at least three measuring devices configured to measure a magnetic field emitted by the cable to be tested, the measuring devices being mounted on the support member in the transverse plane and angularly distributed at the same radial distance from the test area, Each measuring device has its own angular position in the transverse plane relative to the test area, and each measuring device is configured to measure an orthoradial component of the magnetic field emitted by the cable under test. The orthoradial component has an amplitude Si defined by the following formula: Si(0i) = C + Al cos (0i + 01) + ei, where: C is the first parameter to be determined, Al is the second parameter to be determined, and ô01 is the third parameter to be determined. a calculator connected to each measuring device, the calculator being configured to: when ei is negligible with respect to the first and second parameters, determine the first, second, and third parameters from the orthoradial components measured by the measuring devices at a given instant, and Determine the value of the electric current flowing through the cable to be tested from: of the first determined parameter, and of the current equation: I = QC, in which Q is a predetermined constant.

[0008] The measurement system according to the invention makes it possible to measure the intensity of an electric current in an electrical cable simply and efficiently by means of a plurality of magnetic field measuring devices. A single series of measuring devices of the same type allows for a measurement system that is simple in design and compact.

[0009] The shape of the support element, which extends over a maximum amplitude of 180° around the test area, allows for current measurement on electrical cables around which it is not possible to mount a system that completely surrounds the cable under test. In particular, current measurement can easily be carried out on a railway catenary while allowing the passage of a pantograph, as well as on a cable mounted, for example, against a wall.

[0010] In addition, thanks to the plurality of measuring devices distributed around the test area, the current measurement is reliable and does not present a risk of being disturbed, even in the presence of electrical cables in the environment of the cable to be tested.

[0011] In one embodiment, the measurement system comprises at least five measuring devices configured to measure a magnetic field emitted by the cable to be tested, • The amplitude of the ortho-radial component measured by each measuring device is defined according to the following formula: Si(0i) = C + Al cos (0i + 01) + ei and ei being equal to A2 cos (2 0i + 02) in which: • A2 is a fourth parameter to be determined, and • Ô02 is a fifth parameter to be determined, • the calculator being configured for: • when ei is non-negligible with respect to the first and second parameters, determine the first, second, third, fourth, and fifth parameters from the orthoradial components measured by the measuring devices at a given instant, and • determine the value of the intensity of the electric current passing through the cable to be tested.

[0012] The current intensity flowing in the cable under test can easily be reliably measured, even in the presence of interfering cables near the cable under test. The five measuring devices provide five equations and five amplitudes, which allow the five parameters to be determined.

[0013] According to one aspect, the measuring devices are uniformly distributed angularly on the support member around the area to be tested. Such a distribution allows for optimal measurement of the electric current intensity regardless of the position of a disturbing electrical cable in the vicinity of the cable under test. A uniform distribution also helps to harmonize magnetic field measurements.

[0014] In one embodiment, the measurement system comprises between six and nine measuring devices, making it possible to ensure reliable measurement, while ensuring redundancy in case of failure of one of the measuring devices, for example.

[0015] Preferably, the test area having a circular shape with an outer radius, the radial distance between each measuring device and the center of the test area is between two and five times the outer radius of the test area. The radial distance between the measuring device and the center of the test area is defined as the radial distance between the centroid of the measuring device and the center of the test area. Such a radial distance allows for reliable reception of the magnetic field emitted by the cable under test, without risk of interference between the measuring devices.

[0016] According to one aspect, the support element has angular symmetry with respect to the test area, so as to allow symmetrical positioning of the measuring devices with respect to the test area. The support element has, for example, a semi-circular cross-section. By "angular symmetry," it is understood that the support element extends at the same radial distance from the test area so as not to disturb the magnetic field. This makes it possible to reliably determine the parameters to be measured by correlating at least the three amplitude equations.

[0017] In a preferred embodiment, each measuring device is a Hall effect sensor, allowing the use of known, simple to use and compact sensors.

[0018] According to one aspect, each measuring device includes a signal amplification element for the generated signal, making it possible to ensure reliable reception by the computer.

[0019] Preferably, each measuring device includes a filtering element configured to remove harmonics from the generated signals, thus limiting any risk of signal interference.

[0020] The invention also relates to an assembly of a cable to be tested and a measurement system as described above, the support member being mounted around the cable to be tested so as to measure the intensity of the electric current passing through the cable to be tested.

[0021] Finally, the invention relates to a method for measuring the intensity of the electric current flowing in a cable to be tested using the measurement system as described above, a cable to be tested being mounted in the area to be tested, the method comprising the steps of: • measure, at a given instant, using each measuring device, an ortho-radial component of the magnetic field emitted by the cable to be tested, • determine at least the first parameter, the second parameter and the third parameter from the measured ortho-radial components having an amplitude defined according to the following formula: Si(0i) = C + Al cos (0i + 01) + ei, and • determine the value of the intensity of the electric current through the cable to be tested from the first parameter and the current equation: I = QC, in which Q is a predetermined constant.

[0022] According to one aspect, when ei is not negligible with regard to the first parameter and the second parameter, the determination step determines the first parameter, the second parameter, the third parameter, the fourth parameter and the fifth parameter. PRESENTATION OF THE FIGURES

[0023] The invention will be better understood upon reading the following description, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0024] The [Fig. 1] is a schematic representation of a cable to be tested and a measurement system according to a first embodiment of the invention.

[0025] The [Fig.2] is a view of the measuring system in a projection plane orthogonal to the axis along which the cable to be tested extends.

[0026] Fig. 3 is a close-up view of a support member and measuring devices of the measuring system of Fig. 2 in the presence of another cable.

[0027] The [Fig.4] is a schematic representation of a measurement system according to a second embodiment of the invention.

[0028] The [Fig.5] is a diagram of the steps of a measurement process according to one embodiment of the invention.

[0029] It should be noted that the figures set out the invention in detail to implement the invention, said figures being of course able to serve to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0030] The invention relates to a system for measuring the intensity of an electric current flowing through an electrical cable under test. The invention is of particular interest for measuring the intensity of an electric current flowing in a railway catenary.

[0031] As is known, in order for a railway vehicle to run, it must be electrically powered. For this purpose, an overhead line known as a "catenary" extends above the railway track and is configured to be connected to at least one pantograph of the rail vehicle. The overhead contact line (catenary) provides electrical power to the rail vehicle. To ensure optimal operation of the rail vehicle, the electrical current flowing through the catenary must be at a predetermined intensity. Therefore, it is necessary to measure this electrical intensity to allow, if necessary, the implementation of specific measures, such as maintenance or adjustments to the power supply.

[0032] The invention will be described hereafter for the measurement of the intensity of an electric current flowing in a railway catenary, but it is understood that the measurement system according to the invention can just as well be used for the measurement of an intensity of electric current flowing in any type of electric cable.

[0033] For the sake of brevity, the term "cable to be tested" refers to the electrical cable to be tested (for example, the catenary) in which it is necessary to measure the intensity of the electric current.

[0034] With reference to [Fig. 1], the cable to be tested CT extends longitudinally along an X axis, laterally along a Y axis, and vertically along a Z axis, so as to form an orthogonal coordinate system (X, Y, Z). Subsequently, the direction of the vertical axis Z, which extends from bottom to top, is defined as shown in [Fig. 1].

[0035] In this example, the test cable CT has the shape of a right circular cylinder. As such, the test cable CT has a circular cross-section in a cutting plane (Y, Z) as shown in [Fig. 3]. It is understood that the test cable CT could alternatively have a different shape.

[0036] In this example, with reference to [Fig. 3], in the (Y, Z) cutting plane, the cable to be tested CT has a predetermined radius R. Furthermore, in this (Y, Z) cutting plane and along the vertical axis Z, oriented from bottom to top, an upper half CT-1 and a lower half CT-2 of the cable to be tested CT are defined.

[0037] A measurement system 1 for measuring the intensity of the electric current flowing through the cable under test CT, according to one embodiment of the invention, will now be described. Advantageously, the measurement system 1 allows for non-contact measurement of the electric current.

[0038] With reference to [Fig.1], the measuring system 1 comprises a support member 2 configured to extend, in a usage configuration, partly around the cable to be tested CT, a plurality of measuring devices 3, mounted on the support member 2, and a computer 4 connected to the measuring devices 3.

[0039] With reference to [Fig. 2], the measuring member 2 extends longitudinally along a principal axis I, laterally along an axis J, and vertically along an axis K, so as to form an orthogonal coordinate system (I, J, K). The support member 2 thus defines a transverse plane (J, K) to the principal axis I. In this example, the transverse plane (J, K) corresponds to a median plane of the support organ 2. For clarity, we subsequently define a plane (I, J) orthogonal to the vertical axis Z and which thus extends horizontally in a usage configuration.

[0040] Preferably, in the operating configuration shown in [Fig. 1], the principal axis I of the measuring element 2 and the longitudinal axis X of the cable under test CT are substantially coincident. In practice, the principal axis I of the measuring element 2 forms an angle of between -5 and 5° with the longitudinal axis X of the cable under test CT.

[0041] According to one aspect, the support member 2 includes a groove 20 extending longitudinally along the principal axis I. The term "groove" refers to a recess formed in the support member 2. The groove 20 is configured to allow the passage of the test cable CT, as shown in [Fig. 1]. In this example, the groove 20 has a semi-cylindrical shape. It is understood that the groove 20 could have a different shape. In practice, the shape of the groove 20 is preferably configured to complement the shape of the test cable CT.

[0042] According to one aspect, the support member 2 is configured to extend, in the transverse plane (J, K), to a maximum extent opposite one half of the cable under test CT, so as to limit the size of the measuring system 1 around the cable under test CT. In other words, the support member 2 is configured to extend, around the periphery of the cable under test CT, in the transverse plane (J, K), at an angle less than or equal to 180°, as shown in [Fig. 2]. In practice, in the operating configuration, the support member 2 is configured to extend only opposite the upper half CT-1 of the cable under test CT, so as to allow the passage of a pantograph mounted on a railway vehicle under the cable under test CT.

[0043] Preferably, the support member 2 has angular symmetry. By "angular symmetry" it is understood that the support member 2 extends at the same radial distance from the test area ZT so as not to disturb the magnetic field.

[0044] In this example, the support member 2 has the shape of a hollow, right-hand circular semi-cylinder. The groove 20 corresponds to the hollow of the circular semi-cylinder. In other words, the support member 2 in this example comprises a semi-circular cross-section. It goes without saying that the support member 2 could alternatively have a different shape, for example, the shape of a parallelepiped with a square cross-section.

[0045] According to one aspect of the invention, again with reference to [Fig. 2], the transverse plane (J, K) includes a test zone ZT. In practice, the test zone ZT extends, in the transverse plane (J, K), into the groove 20. In other words, the cable to be tested, CT, is configured to extend into the test zone ZT during its use. In this example, the test zone ZT has a circular shape with an outer radius RE. In practice, the test zone ZT has a shape complementary to the cable under test CT. Thus, preferably, the outer radius RE of the test zone ZT is substantially equal to the radius R of the cable under test CT, as shown in [Fig. 3].

[0046] Preferably, the support member 2 is made of a non-magnetic material so as not to interfere with the magnetic field emitted by the cable under test CT and therefore with the current measurement. The support member 2 is therefore preferably made of a plastic material, for example, Plexiglas or an Acrylonitrile Butadiene Styrene (ABS) polymer. The support member 2 is thus also lightweight.

[0047] In the operating configuration, the support member 2 is held above the cable under test CT by mounting members (not shown), in particular, clamps or gripping jaws mounted on the catenary. Such gripping jaws are known to those skilled in the art, for example, for fixing a catenary support pendulum to railway tracks.

[0048] To enable the measurement of the current intensity of the cable to be tested CT, the measuring system 1 comprises a plurality of measuring devices 3.

[0049] Each measuring device 31, 32, 33 is configured to measure a magnetic field emitted by the cable under test CT. In this example, the measuring devices 31, 32, 33 are Hall effect sensors. Such sensors are known to those skilled in the art, and their operation will not be described in further detail in this document. It is understood that the measuring devices 31, 32, 33 could be in a different form, for example, coils for measuring alternating current, magnetoresistive magnetometers, or fluxgate type sensors.

[0050] For the sake of brevity, the reference to the measuring devices 31, 32, 33 will generally be denoted 3i.

[0051] With reference to [Fig. 2], the measuring devices 3i are mounted on the support member 2 in the transverse plane (J, K) and positioned at the same radial distance D from the test area ZT. In practice, the radial distance D corresponds to the distance measured radially between the centroid of the measuring device 3i and the center B of the test area ZT. In other words, the centroids of the measuring devices 3i form an arc AC around the test area ZT. In this example, the radial distance D between the center B of the test area ZT and the arc AC corresponds to two to five times the outer radius RE of the test area ZT, so as to ensure a reliable measurement. The measuring devices 3i are also oriented radially towards the test area ZT.

[0052] Preferably, the measuring devices 3i are distributed angularly around the test area ZT. In practice, the measuring devices 3i are distributed along the arc of a circle AC. In other words, the measuring devices 3i are distributed, in this example, over an angular range of 180° around the test area ZT. Preferably, the measuring devices 3i are evenly distributed on the support member 2 around the test area ZT.

[0053] With further reference to [Fig. 2], each measuring device 3i has its own angular position 0i in the transverse plane (J, K) relative to the test area ZT. More precisely, the angular position 0i corresponds to the angular position of the centroid of the measuring device 3i in question. In this example, the angular position 0i of each measuring device 3i is measured in the transverse plane (J, K) relative to an origin position O on the arc of a circle AC forming a zero angle with the horizontal plane (I, J), as shown in [Fig. 2].

[0054] According to one aspect, again with reference to [Fig. 2], the measurement system 2 comprises at least three measuring devices 3i. In practice, the number of measuring devices 3i depends on the presence or absence of one or more electrical cables positioned near the cable under test CT and likely to interfere with the current measurement. Such a cable, one of which is shown in [Fig. 3], will be referred to hereafter as the "interference cable CP".

[0055] Preferably, when the interfering cable CP is positioned at a distance from the cable to be tested CT (measured in the transverse plane (J, K)) greater than or equal to ten times the radial distance D between the arc of the circle AC and the test area ZT, the measuring system 1 comprises three measuring devices 31, 32, 33, as shown in Figures 2 and 3. Also, in this example in which the support member 2 has the shape of a portion of a disk extending over 180°, the measuring devices 31, 32, 33 are preferably distributed angularly every 60°, for example at 30°, 90° and 150° from the original position O.

[0056] Alternatively, with reference to [Fig. 4], when the interfering cable CP is positioned at a distance from the cable under test CT (measured in the transverse plane (J, K)) strictly less than ten times the radial distance D (between the arc of a circle AC and the test area ZT), the measuring system 1 comprises five measuring devices 31, 32, 33, 34, 35. Also, in this example in which the support member 2 has the shape of a portion of a disk extending over 180°, the measuring devices 31, 32, 33, 34, 35 are preferably distributed angularly every 30°, for example at 30°, 60°, 90°, 120° and 150° from the origin position O. The measuring system 1 could alternatively comprise a number of measuring devices 3i greater than five, for example a number between six and nine, in order to ensure a reliable current measurement with redundancies.

[0057] According to one aspect of the invention, as described above, each measuring device 3i is configured to measure an orthoradial component COi of the magnetic field emitted by the cable under test CT. Each orthoradial component COi has an amplitude Si defined according to the following formula: S;(0i) = C + Al cos (0; + Ô01) + Ei, in which C is a first parameter to be determined, Al is a second parameter to be determined and ô01 is a third parameter to be determined.

[0058] Furthermore, criterion e; is equal to A2 cos (2 0i + Ô02), in which A2 is a fourth parameter to be determined and Ô02 is a fifth parameter to be determined.

[0059] In practice, each measuring device 3i is configured to receive the orthoradial component CO of the magnetic field emitted by the cable under test CT and to emit a signal representative of this orthoradial component. The amplitude Si of the emitted signal is received by a computer 4.

[0060] In one embodiment, each measuring device 3i includes an amplification element, configured to increase the amplitude Si of the signal emitted in response to the received ortho-radial component CO.

[0061] Preferably, each measuring device 3i includes a filtering element, so as to remove harmonics from the generated signals and to improve the quality of the signal received by the computer 4. It goes without saying that other processing steps could be implemented to improve the acquisition of the amplitude Si.

[0062] With reference to [Fig. 2], calculator 4 is connected to each measuring device 3i and is configured to receive, at a given time t, from each measuring device 3i, the amplitude Si of each ortho-radial component COi. In other words, calculator 4 is configured to receive a plurality of amplitudes Si, each being a function of the angular positioning 0; and defined according to the formula described above.

[0063] In particular, when a disturbing cable CP is considered to be far from the test area ZT (i.e., positioned at a distance from the test area ZT greater than or equal to ten times the radial distance D), the criterion e; is considered negligible compared to the first parameter C and the second parameter Al. The measurement system 1 comprises three measuring devices 31, 32, 33. The computer 4 is configured to receive three amplitudes Si, S2, S3 of ortho-radial components COi: S^OJ = C + Al cos (0! + Δ01), S2(02) = C + Al cos (02 + Δ01), and S3(03) = C + Al cos (03 + Δ01).

[0064] When the interfering cable CP is considered to be close to the test area ZT (i.e., positioned at a distance from the test area ZT less than ten times the radial distance D), the criterion e; is considered non-negligible compared to the first parameter C and the second parameter AL. The measurement system 1 comprises, in this example, five measuring devices 31, 32, 33, 34, 35. The calculator 4 is configured to receive five amplitudes Si, S2, S3, S4, S5 with ortho-radial components COi: Si (0i) = C + Al cos (0! + Δ01) + A2 cos (2 0! + Δ02), S2(02) = C + Al cos (02 + Δ01) + A2 cos (2 02 + Ô02), S3(03)= C + Al cos (03 + Ô01) + A2 cos (2 03 + Ô02), S4(04) = C + Al cos (04 + 001) + A2 cos (2 04 + Ô02), S5(05) = C + Al cos (05 + Ô01) + A2 cos (2 05 + Ô02).

[0065] From the signals Si received from the measuring devices 3i, the computer 4 is configured to determine the first parameter C, the second parameter Al, and the third parameter ô01 when e; is negligible. Indeed, the three unknown parameters can be easily determined from the three equations provided by the three measuring devices 3i.

[0066] From the signals Si received from the measuring devices 3i, the computer 4 is configured to determine the first parameter C, the second parameter A1, the third parameter 01, the fourth parameter A2, and the fifth parameter 02 when e is non-negligible. Indeed, the five unknown parameters can be easily determined from the five equations provided by the five measuring devices 3i.

[0067] According to one aspect, the calculator 4 is then configured to determine the value of the current intensity I flowing through the cable under test CT from the first determined parameter C and the current equation: I = Q C. In this equation, Q is a predetermined constant. In this example, Q is determined by calibrating the measuring system 1 by placing it around an electrical cable carrying a known current.

[0068] In one embodiment, the measuring system 1 includes a multiplexer, mounted between the measuring devices 3i and the computer 4 to facilitate the communication of the signals Si to the computer 4.

[0069] Thanks to the measuring system 1, the intensity of the electric current can advantageously be measured, even in the presence of one or more interfering cable(s) CP. The shape of the measuring system 1 allows it to be mounted on an electric cable where space is limited. Thus, electric current measurement can be carried out on a railway catenary, while still allowing the passage of a pantograph.

[0070] A method for measuring the intensity of an electric current flowing in an electrical cable under test CT, with reference to [Fig. 5], will now be described. The measurement method is implemented using a measuring system 1 as described previously and shown in [Fig. 4]. The cable under test CT extends into the groove 20 of the support member 2 and is thus mounted in the test zone ZT, which has an outer radius RE. In this example, a disturbing cable CP is located in the vicinity of the cable under test CT and is positioned at a distance from the test zone ZT less than ten times the radial distance D between the center B of the zone and test ZT and the arc of a circle AC formed by the centroids of the measuring devices 3i. In this example, the measurement system 1 comprises five measuring devices 31, 32, 33, 34, 35 distributed angularly and uniformly around the test area ZT and positioned at the same radial distance D from the test area ZT. Each measuring device 31, 32, 33, 34, 35 has a predetermined angular position 0b 02, 03, 04, 05.

[0071] Due to the flow of electric current, the cable to be tested CT emits a magnetic field which is received by the measuring devices 3i. The measuring devices 3i being distributed angularly around the test area ZT at the same radial distance D, they receive the magnetic field simultaneously.

[0072] In a first step El, at a given instant t, each measuring device 3i measures an ortho-radial component COi of the magnetic field emitted by the cable to be tested CT. Each ortho-radial component COi is received by the computer 4, which is connected to each measuring device 3i, for example by a data network.

[0073] In a second step E2, the calculator 4 determines, for each received ortho-radial component COi, an amplitude Si. The calculator 4 then determines, in this example, the following plurality of equations: Si(0i) = C + Al S2(O2) = C + Al S3(O3) = C + Al S4(04) = C + Al S5(05) = C + Al cos (0i + Ô01) + A2 cos (2 0i + Ô02), cos (02 + Ô01) + A2 cos (2 02 + Ô02), cos (03 + Ô01) + A2 cos (2 03 + Ô02), cos (04 + Ô01) + A2 cos (2 04 + Ô02), cos (05 + Ô01) + A2 cos (2 05 + Ô02).

[0074] The process then includes, a third step E3 in which the calculator 4 determines, from the amplitudes Si measured by each measuring device 3i, the first parameter C, the second parameter Al, the third parameter Ô01, the fourth parameter A2, the fifth parameter Ô02.

[0075] Once the first parameter C is determined, the calculator 4 determines, in a fourth step E4, the intensity of the electric current flowing in the cable under test CT, from the current equation according to which I = Q x C. In this example, the coefficient Q has been previously determined by mounting the measuring system 1 on an electric cable whose intensity is known. This step is carried out in a manner analogous to the measurement of the current in the cable under test CT, only the parameter to be determined in the current equation differs.

[0076] Thanks to the measuring system according to the invention, the electric current intensity can be measured simply using a compact system that can be used on a railway catenary. Due to the number of measuring devices and by using a measured ortho-radial component amplitude, the measurement is advantageously reliable, even in the presence of an electrical cable nearby.

Claims

1. Demands A measuring system (1) for the intensity of electric current flowing in an electrical cable to be tested, hereinafter referred to as the cable to be tested (CT), the measuring system (1) comprising: • a support member (2) comprising a groove (20) extending longitudinally along a principal axis (I) and configured to allow passage of the cable to be tested (CT), the support member (2) defining a transverse plane (J, K) to the principal axis (I) which includes a test zone (ZT), the support member (2) extending, in the transverse plane (J, K), over an angular range around the test zone (ZT) less than or equal to 180°, the cable to be tested (CT) being configured to extend into the test zone (ZT) during its use, • at least three measuring devices (31, 32, 33) configured to measure a magnetic field emitted by the cable to be tested (CT), the measuring devices (31, 32, 33) being mounted on the support member (2) in the transverse plane (J, K) and angularly distributed at the same radial distance (R) from the test area (ZT), • each measuring device (3i) having its own angular position (0i) in the transverse plane (J, K) relative to the test zone (ZT), each measuring device (3i) being configured to measure an orthoradial component (CO) of the magnetic field emitted by the cable to be tested (CT), the orthoradial component (CO) having an amplitude (Si) defined according to the following formula: Si(0i) = C + Al cos (0i + 01) + e; in which: • C is a first parameter to be determined, • Al is a second parameter to be determined, and • ô01 is a third parameter to be determined, • a calculator (4) connected to each measuring device (3), the calculator (4) being configured to: • when e; is negligible with respect to the first parameter (C) and the second parameter (Al), determine the first parameter (C), the second

2.

3. parameter (Al) and the third parameter (ô01) from the ortho-radial components C(O) measured by the measuring devices (3i) at a given time (t), and • determine the intensity value (I) of the electric current through the cable to be tested (CT) from: • the first parameter (C) determined, and • the current equation: I = QC, in which Q is a predetermined constant. Measurement system (1) according to claim 1, wherein the measurement system (1) comprises at least five measuring devices (3) configured to measure a magnetic field emitted by the cable to be tested (CT), • the amplitude (Si) of the ortho-radial component (CO) measured by each measuring device (3i) being defined according to the following formula: Si(0i) = C + Al cos (0i + 01) + ei and ei being equal to A2 cos (2 0i + 02) in which: • A2 is a fourth parameter to be determined, and • Ô02 is a fifth parameter to be determined, • the calculator (4) being configured for: • when ei is non-negligible with respect to the first parameter (C) and the second parameter (Al), determine the first parameter (C), the second parameter (Al), the third parameter (O01), the fourth parameter (A2) and the fifth parameter (O02) from the orthoradial components (CO) measured by the measuring devices (3i) at a given time (t), and • determine the intensity value (I) of the electric current flowing through the cable to be tested (CT). Measurement system (1) according to any one of claims 1 to 2, wherein the measuring devices (3i) are uniformly distributed angularly on the support member (2) around the area to be tested (ZT).

4. Measurement system (1) according to any one of claims 1 to 3, wherein the measurement system (1) comprises a number of measuring devices (3i) between six and nine.

5. Measurement system (1) according to any one of claims 1 to 4, wherein, the test area (ZT) having a circular shape having an outer radius (RE), the radial distance (D) between each measuring device (3i) and the center (B) of the test area (ZT) is between two and five times the outer radius (RE) of the test area (ZT).

6. Measurement system (1) according to any one of claims 1 to 5, wherein the support member (2) has angular symmetry with respect to the test area (TA), so as to allow symmetrical positioning of the measuring devices (3) with respect to the test area (TA).

7. Measurement system (1) according to any one of claims 1 to 6, wherein each measuring device (3) is a Hall effect sensor.

8. Assembly of a test cable (CT) and a measuring system (1) according to any one of claims 1 to 7, the support member (2) being mounted around the test cable (CT) so as to measure the intensity of the electric current through the test cable (CT).

9. A method for measuring the intensity of the electric current flowing in a test cable (CT) by means of the measuring system (1) according to any one of claims 1 to 7, a test cable (CT) being mounted in the test zone (ZT), the method comprising the steps of: • Measuring (E1), at a given time (t), by each measuring device (3i), an orthoradial component (CO) of the magnetic field emitted by the test cable (CT), • determining (E3) at least the first parameter (C), the second parameter (A1) and the third parameter (Δ01) from the measured orthoradial components (CO) having an amplitude (Si) defined according to the following formula: Si(Δi) = C + Al cos (Δi + Δ01) + Ei, and • determining (E4) the value of the intensity (I) of the electric current flowing through the test cable (CT) from the first parameter (C) and the current equation: I = QC, where Q is a predetermined constant.

10. Measurement method according to claim 9, wherein, when ei is non-negligible with respect to the first parameter (C) and the second parameter (Al), the determination step (E3) determines the first parameter (C), the second parameter (Al), the third parameter (O01), the fourth parameter (A2) and the fifth parameter (O02).

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