Method and device for simultaneously measuring the intensity of the current in each phase of a polyphase electric cable

Abstract

The invention relates to a method and device for simultaneously measuring the intensity of the current in the N conductors of a cable, which method comprises placing (E1), around the cable, k sets of N magnetic sensors with an angular offset between the sensors; computing (E4) a plurality of inverse matrices corresponding to different positions of the sensors relative to the cable, each inverse matrix M-1 being computed after having measured (E2), by means of the N x k sensors, the magnetic field produced by the current flowing in each conductor and after having determined (E3) the angle between each conductor and the closest sensor; deducing (E5) therefrom, for each inverse matrix M-1, the values of the intensities I = (µ0 / 2π).M-1.B, where B is the matrix of the magnetic fields and µ0 is a magnetic permeability; and selecting (E6) the inverse matrix which corresponds to the minimum of the difference between the matrices of the intensities obtained in the deduction step (E5).

Description

Description Title of the invention: METHOD AND DEVICE FOR SIMULTANEOUSLY MEASURING THE CURRENT INTENSITY IN EACH PHASE OF A POLYPHASE ELECTRIC CABLE

[0001] The present invention relates to a method and a device for simultaneously measuring the intensity of the instantaneous current in each phase of a polyphase electric cable, alternating or direct current.

[0002] The invention belongs to the field of electrical cables intended for the transport of energy and / or the transmission of data. It finds application in particular in the field of optimizing energy distribution in buildings.

[0003] Currently, to measure the instantaneous current intensity in each conductor of a polyphase or multi-conductor cable, most often, the current intensity in each of the conductors is measured successively using an ammeter clamp.

[0004] However, these operations are time-consuming and generally provide imprecise results.

[0005] There is no practical technical solution on the market that allows the current intensity in all conductors of a multi-phase cable to be measured simultaneously, quickly and accurately.

[0006] The present invention aims to remedy the aforementioned drawbacks of the prior art.

[0007] For this purpose, the present invention proposes a method for measuring the current intensity in an electric cable comprising N conductors, N being an integer greater than or equal to 2, remarkable in that it consists of simultaneously measuring the current intensity in each of the N conductors by carrying out steps consisting of: - placing a set of magnetic field sensors around the cable, at least in one location along the length of the cable, this set of sensors comprising k sets of N sensors, k being an integer greater than or equal to 2, the N x k sensors of this set being distributed on a circle and the N sensors having between them an angular offset less than or equal to 2TT / N; - calculate a plurality of inverse matrices M -1 each corresponding to a different position of the set of sensors relative to the cable, each position of the set of sensors relative to the cable being defined, by assimilating the conductors and the sensors to points and the N conductors being located on a circle, by: - the angle between a conductor and the nearest sensor among the N xk sensors of the aforementioned set, this angle being defined relative to the center of the circle on which the sensors are located; - the Cartesian coordinates of the center of the circle on which the sensors are located, in a Cartesian frame of reference having as its origin the center of the circle on which the conductors are located and - the radius of the circle on which the conductors are located, each inverse matrix M -1 being calculated following the steps consisting of: - simultaneously measure, for each of the N conductors, at least one component of the magnetic field produced by the current flowing in the conductor, by means of the set of N xk magnetic field sensors; and - for each of the N conductors, determine the angle between this conductor and the nearest magnetic field sensor, the intensities of the currents in the conductors being linked to the components of the magnetic field measured by the relation B = pMI where B is the matrix of the components of the magnetic field, I is the matrix of the intensities of the currents, M is a matrix comprising a plurality of proportionality coefficients depending on the angles between the conductors and the magnetic field sensors and p is a predetermined coefficient; - following the step of calculating the plurality of inverse matrices M' 1 , deduce , for each inverse matrix M -1 , the values ​​of the current intensities I = (po / 2n).M' 1 .B, where po is an equivalent magnetic permeability which takes into account the presence of insulating materials in the cable; and - select, from the plurality of inverse matrices M -1calculated in the above-mentioned calculation step, the inverse matrix which corresponds to the minimum value of the difference between the matrices of the current intensities obtained in the step of deduction for each position of the set of sensors relative to the cable, the current intensity in each of the N conductors of the cable being the value obtained via the inverse matrix calculated in the calculation step and selected in the selection step.

[0008] Thus, the invention makes it possible to measure the current intensity in all the conductors of the cable in a single operation and to quickly obtain extremely accurate results, without the need to remove the cable sheath. Furthermore, the installation of the magnetic field sensors around the cables is easy and does not cause any damage, marks or deformation to the cables. Furthermore, since the position of the magnetic field sensors relative to the conductors of the cable is unknown, taking into account the angular offset between sensors and conductors makes it possible to increase the accuracy of the intensity values ​​obtained. Furthermore, there is no need to store or have access to a library of matrices, since the plurality of inverse matrices has not been constructed prior to the execution of the method, but is calculated each time the method is implemented.

[0009] Furthermore, the number N xk of sensors, combined with the calculation of the plurality of inverse matrices M -1 and the selection of the "best" matrix, in the sense that the residual difference in the calculation of the current intensities is the smallest, makes it possible to obtain increased precision in the measurement of the intensities of the currents which circulate in each of the N conductors of the electric cable.

[0010] The invention offers numerous applications, such as the identification of unbalanced current distributions which sometimes reveal a faulty power supply, the anticipation of cable failures when a conductor reaches an excessive temperature or even the reduction of electrical energy consumption in an installation.

[0011] In a particular embodiment, the measuring step consists of simultaneously measuring, for each of the conductors, the tangential component and / or the radial component of the magnetic field produced by the current flowing in the conductor, by means of the set of N xk magnetic field sensors.

[0012] This makes it possible to minimize the error in the intensity values ​​obtained, i.e. to further increase the precision of these values.

[0013] In a particular embodiment, the N sensors have an angular offset of 2TT / N between them.

[0014] This enables particularly high resolution in intensity measurements, ensuring high measurement accuracy.

[0015] In a particular embodiment, the k sets of sensors have between them an angular offset of 2n7(kx N).

[0016] For the same purpose as that indicated above, the present invention also proposes a device for measuring the current intensity in an electric cable comprising N conductors, N being an integer greater than or equal to 2, remarkable in that it comprises: the set of N xk magnetic field sensors mentioned above, k being an integer greater than or equal to 2; a processing means adapted to receive the values ​​of the components of the magnetic field and to apply the steps of angle determination, calculation of inverse matrices, deduction of values ​​of the current intensities and selection included in a method as described succinctly above.

[0017] In a particular embodiment, the device further comprises a housing containing the set of N xk magnetic field sensors.

[0018] This makes it easier to install the device around the cable, as it is not necessary to install each sensor individually.

[0019] In a particular embodiment, the housing is surrounded by electromagnetic shielding.

[0020] This prevents the penetration of electromagnetic disturbances due, for example, to the Earth's permanent magnetic field and possible sources of electromagnetic fields located near the cable and sensors.

[0021] In a particular embodiment, the housing has a section formed of two half-rings, suitable for positioning the device around the cable.

[0022] This configuration allows for rapid installation of the device around the cable, which is therefore housed in the center of the circular opening formed by the meeting of the two half-rings.

[0023] In a particular embodiment, the device further comprises at least one additional magnetic field sensor adapted to measure the Earth's magnetic field.

[0024] This allows the value of the Earth's magnetic field to be taken into account, which can then be subtracted when processing the magnetic field values ​​collected by the sensors.

[0025] In a particular embodiment, the at least one additional sensor is arranged inside the housing and / or outside the housing.

[0026] Still with the same aim as that indicated above, the present invention also proposes an electric cable arrangement comprising an electric cable comprising N conductors, N being an integer greater than or equal to 2, this arrangement being remarkable in that it further comprises at least one device as succinctly described above placed around the cable.

[0027] In a particular embodiment, the electrical cable arrangement comprises a plurality of devices as briefly described above, placed around the cable at predetermined intervals from each other.

[0028] This ensures adequate measurement of current intensities in the cable conductors in the event that these conductors are twisted in such a way that they are likely to influence the sensitivity of the current measurement.

[0029] Other particular features and advantages of the device and the electrical cable arrangement being similar to those of the method, they are not repeated here. Brief description of the drawings

[0030] Other aspects and advantages of the invention will appear on reading the detailed description below of particular embodiments, given as non-limiting examples, with reference to the appended drawings, in which:

[0031] [Fig. 1] is a flowchart illustrating steps of a method according to the present invention, in a particular embodiment.

[0032] [Fig. 2] is a geometric representation illustrating different parameters used in a method according to the present invention, in a non-limiting example where the electric cable considered comprises five conductors.

[0033] [Fig. 3] is a schematic representation of an electrical cable device and arrangement according to the present invention, in a particular embodiment.

[0034] [Fig. 4] is a schematic representation of an electrical cable arrangement according to the present invention, in another particular embodiment.

[0035] [Fig. 5] another geometric representation illustrating different parameters used in a method according to the present invention, in a non-limiting example where the electric cable considered comprises five conductors. Description of embodiment(s)

[0036] The present invention considers a polyphase, or multi-conductor, alternating or direct current cable. N denotes the number of conductors in the cable. N is an integer greater than or equal to 2. These conductors are not necessarily identical.

[0037] The invention is based on the local measurement of at least one component of the magnetic field emitted by the current sources, which are here the N conductors, by means of magnetic field sensors.

[0038] In short, since a polyphase cable has several current densities coming from its N conductors, we can first calculate the magnetic field produced by the current using the Biot-Savart law, then invert all the local measurements of the magnetic field components by determining an inverse matrix, in order to obtain the current intensities coming from the N current sources.

[0039] Thus, as shown in the flowchart of Figure 1, the method, in accordance with the invention, for measuring the current intensity in an electric cable comprising N conductors, consists of simultaneously measuring the current intensity in each of the N conductors, as detailed below.

[0040] A first step E1 consists of placing a set of magnetic field sensors around the cable, at at least one location along the length of the cable. The set of sensors comprises k sets of N sensors, k being an integer greater than or equal to 2, i.e. K sets of magnetic field sensors each comprising N magnetic field sensors.

[0041] As a non-limiting example, we can choose k = 2, in other words a set of sensors consisting of a first set of N sensors and a second set of N sensors, so that in this non-limiting example, there are twice as many sensors as conductors.

[0042] The N xk sensors of the sensor set are distributed on a circle Ts, of radius R, as illustrated in Figure 5.

[0043] There may be an angular offset between the sensors of each set of N sensors, in other words, it is possible not to position two sets of sensors in the same way relative to the cable. This makes it possible to multiply the measurements in order to increase the precision of the value of the intensities which will be obtained at the end of the execution of all the steps of the method according to the present invention. In this case, the N sensors have between them an angular offset of between 0 and 2TT / N, that is to say that this angular offset is less than or equal to 2TT / N.

[0044] Advantageously, the angular offset between the N sensors is 2TT / N.

[0045] Advantageously, the angular offset between each set of N sensors is 2n7(kx N).

[0046] Step E1 may for example consist of fixing around the cable one or more devices according to the invention, each device containing all or part of the aforementioned set of sensors. The device according to the invention is described further with reference to Figures 3 and 4.

[0047] During the operation of installing one or more devices according to the invention in step E1, no movement is required, neither of the device(s), nor of the cable, nor of the device(s) relative to the cable or vice versa, whether whether it is a translational movement, a rotational movement, or any other movement. Furthermore, there is no constraint regarding the knowledge or application of the intensity values ​​of the electric current flowing in the conductors of the cable.

[0048] Then a step E2 consists of simultaneously measuring, for each of the N conductors of the cable, at least one component of the magnetic field produced by the current flowing in this conductor.

[0049] These simultaneous measurements are carried out using the set of N xk magnetic field sensors.

[0050] In a particular embodiment, the set of magnetic field sensors can measure for each conductor only the tangential component or only the radial component of the magnetic field.

[0051] Alternatively, for greater accuracy, the magnetic field sensor assembly can measure for each conductor both the tangential and radial components of the magnetic field.

[0052] Then, in a step E3, for each of the conductors, the angle a is determined between this conductor and the nearest magnetic field sensor among the N xk sensors of the set of magnetic field sensors. The angle a is defined with respect to the center of the circle Ts on which the sensors are located, by assimilating the conductors and the sensors to points. As indicated above, the sensors are located on a circle Ts. In addition, the conductors are located on a circle Te. Indeed, for simplicity, we assume that each conductor has an infinitely small section and that the magnetic field captured by each sensor is located at a point corresponding to the location of the sensor.

[0053] Figures 2 and 5 schematically illustrate, by way of non-limiting example, a cable of circular section comprising five conductors regularly distributed inside the cable, which are assimilated to five points C1 to C5 equidistant from each other on the circumference of a circle Te. Only the magnetic field sensor closest to the conductor C1 has been shown and is symbolized by point A in Figure 2 and by point Si in Figure 5. The radius of the circle Te is designated by r, the distance between the conductor Ci and the sensor A is denoted by di in Figure 2 and the corresponding distance between conductor Ci and sensor Si is denoted by dij in Figure 5, the straight line segment connecting sensor A and the center of circle Te is denoted by d'i in Figure 2, the angle at point A between the straight line segment d'i and the straight line segment connecting conductor C1 and point A is denoted by 0 in Figure 2 and the same angle is denoted by 5i,j in Figure 5. In Figure 2, the magnetic field picked up by sensor A is represented by the vector Bi , which is orthogonal to the straight line segment connecting conductor C1 and point A and in Figure 5, the same magnetic field is represented by the vector Btot. whose tangential component is represented by the vector B T and the radial component is represented by the vector B p .

[0054] For a cable comprising N conductors each producing a magnetic field Bi, i = 1, N, the component BA of the magnetic field at point A coming from the N conductors is defined as follows:

[0055] [Math. 1]

[0057] Or : Bim is the component of the magnetic field coming from the i ème driver captured by the rn ième sensor; angles ai and Pi are defined for the i ème conductor similarly to the angles a and p defined above, respectively; di denotes the distance between the i ème conductor and the nearest sensor; po is an equivalent magnetic permeability which takes into account the presence of insulating materials in the cable; r is as defined above the radius of the circle Te; and hm is the value of the intensity of the current flowing in the i ème conductor and deduced from the magnetic field measurement carried out by the m ième sensor.

[0058] Thus, the current intensities in the conductors are linked to the measured magnetic field components, by the relation B = pMI where B is the matrix of the magnetic field components measured in all the conductors by all the sensors, I is the matrix of the current intensities circulating in all conductors, M is a matrix comprising a plurality of proportionality coefficients depending on the angles between the conductors and the magnetic field sensors and p is a predetermined coefficient.

[0059] It follows that I = (po / 2n).M' 1 .B, where M -1 is the inverse matrix of M.

[0060] Thus, as shown in Figure 1, following steps E2 of measuring and E3 of determining the angle a between each conductor and the nearest sensor, a step E4 is carried out consisting of calculating a plurality of inverse matrices M -1each corresponding to a different position of the sensor assembly relative to the cable.

[0061] Each position of the sensor set relative to the cable is defined by: - the angle between a conductor and the nearest sensor among the N xk sensors of the set of sensors, this angle being defined relative to the center of the circle Ts on which the sensors are located; - the Cartesian coordinates (x e xc,yexc), represented in Figure 5, from the center of the circle Ts on which the sensors are located, in a Cartesian reference frame having as its origin the center of the circle Te on which the conductors are located (the center of the circle Te therefore having (0,0) for Cartesian coordinates, as represented in Figure 5); and - the radius r of the circle Te on which the conductors are located.

[0062] The calculation of the plurality of inverse matrices M -1at step E4 allows us to deduce, at the following step E5, for each inverse matrix M -1 , values ​​of the intensities of the currents I = (po / 2n .M' 1 .B in all conductors of the cable.

[0063] Then, during a step E6, the matrices giving values ​​of the intensities of the currents I obtained in the deduction step E5 are compared with each other and, from the plurality of inverse matrices M, are selected. -1 calculated in step E4 of calculation, the inverse matrix M -1 which corresponds to the minimum value of the difference between the matrices of the intensities of the currents I obtained in step E5.

[0064] The value retained for the current intensity in each of the N conductors of the cable is therefore the value obtained via the inverse matrix M -1 calculated in calculation step E4 and selected in selection step E6.

[0065] As a non-limiting example, for N = 5 conductors and k = 2, i.e. two sets of five magnetic field sensors placed respectively at points A, B, C, D and E for the first set of sensors and A', B', C', D' and E' for the second set of sensors, the analytical expression making it possible to deduce the intensities of the currents in the conductors by the first set of sensors A, B, C, D and E is as follows:

[0066] [Math. 2]

[0068] where I i , i = 1 , ... , 5 denotes the intensity of the current flowing in the i ème conductor and BA, BB, BC, BD and BE denote the magnetic field components respectively measured by the five sensors of the first set of sensors.

[0069] The equivalent magnetic permeability po is a macroscopic permeability, which makes the calculation simpler than if we considered the local magnetic permeability.

[0070] The second set of 5 sensors A', B', C', D' and E' is positioned on the same circle Ts as the first set of 5 sensors A, B, C, D and E and the 5 sensors of each set are angularly offset from each other by an angle less than or equal to 2TT / 5. In addition and by way of non-limiting example, the angular offset between these two sets of sensors can be TT / 5. This makes it possible to obtain very good resolution in the measurement of intensities and therefore high measurement precision.

[0071] For the second set of sensors A', B', C', D' and E', in step E4, another matrix M is calculated -1 similar to that given above in the detail of the relation l= (PO / 2TT).M- 1 .B.

[0072] If we denote by I the matrix of intensities deduced from the first set of sensors A, B, C, D and E and l' the matrix of intensities deduced from the second set of sensors A', B', C', D' and E', step E6 includes an operation consisting of comparing I and I'. The parameters corresponding to the installation of the device for measuring the current intensity in the cable considered will be those which will give the minimum difference between I and I'.

[0073] In a particular embodiment, the angle α between a conductor and the nearest magnetic field sensor is determined so as to maximize the following function F:

[0074] [Math. 3]

[0076] where h denotes the intensity of the current flowing in the i ème driver.

[0077] There are various known mathematical convergence methods for maximizing F, such as the Levenberg-Marquardt algorithm (also called the LM algorithm) or the Nelder-Mead method.

[0078] As shown in Figure 3, a device 30 according to the present invention, for measuring the current intensity in an electric cable 32 comprising N conductors 34, N being the aforementioned integer greater than or equal to 2, comprises the aforementioned set of N xk magnetic field sensors 36, k being the aforementioned integer greater than or equal to 2. In the non-limiting example illustrated, the set of sensors 36 consists of two sets of five sensors each, one set being illustrated in solid lines and the other set being illustrated in dashed lines.

[0079] The device 30 also comprises a processing means 38 adapted to receive the values ​​of the components of the magnetic field measured by the set of sensors 36 and to apply the steps E3 of angle determination, E4 of inverse matrix calculation, E5 of deduction of values ​​of the current intensities and E6 of selection included in the method described above, in order to deduce a value of the intensity of the current flowing in each of the conductors 34 with increased precision.

[0080] The processing means 38 may be located either in the device 30 or remotely therefrom, a communication means then being provided to transmit the values ​​of the measured components of the magnetic field from the sensors 36 to the processing means 38. When it is located remotely from the device 30, the processing means 38 may be located in a laptop or other computer, a tablet, a smartphone or other mobile means of communication, or even be located in the cloud.

[0081] In the particular embodiment illustrated, the device 30 further comprises a housing 31 containing the set of N xk magnetic field sensors 36. Such a housing is optional, the sensors 36 being able to be placed around the cable without being contained in any enclosure.

[0082] In the particular embodiment illustrated, the housing 31 has a section formed by two half-rings 311 and 312, adapted to the positioning of the device 30 around the cable 32, the two half-rings 311 and 312 defining by their assembly an opening in which the cable 32 passes. In the particular embodiment illustrated, the cable 32 has a circular section and the opening formed by the two half-rings 311 and 312 is also circular and of diameter slightly greater than that of the section of the cable.

[0083] Once the device 30 is placed around the cable 32, the two half-rings 311 and 312 can be connected to each other, for example, by means of a hinge-type joint, or can be secured to each other, for example, by means of screws or nuts or other preferably removable fixing means.

[0084] Also optionally, the housing 31 can be surrounded by electromagnetic shielding preventing the sensors from being disturbed by any surrounding sources of electromagnetic waves as well as by the Earth's permanent magnetic field. This shielding can be made, for example, of a specific steel.

[0085] Whether such shielding is present or not, the device 30 may further be equipped with one or more additional magnetic field sensors 37 adapted to measure in particular the Earth's magnetic field, in order to subtract the value of the latter when processing the values ​​of the components of the magnetic field measured by the magnetic field sensors 36. The additional sensor(s) 37 may be arranged inside and / or outside the housing 31, or even directly around the cable when there is no housing.

[0086] Thus, an electrical cable arrangement according to the present invention comprises the cable 32 comprising N conductors 34, N being the aforementioned integer greater than or equal to 2 and at least one device 30 placed around the cable 32.

[0087] As shown in the particular embodiment of Figure 4, the electrical cable arrangement may comprise a plurality of devices 30, placed around the cable 32 at predetermined intervals from each other.

[0088] The processing means 38 may be unique and common to all the devices 30. Alternatively, a processing means 38 may be provided for each device 30 and communication means adapted to communication between the various processing means 38 may possibly be provided.

[0089] In the particular embodiment illustrated, the devices 30 are all identical, each comprise two sets of five magnetic field sensors 36 and are arranged at regular intervals along the cable 32.

[0090] Such a configuration makes it possible to guarantee high-quality measurement of current intensities even in the case where the conductors 34 are twisted, for example due to manufacturing conditions and / or specific constraints, which could influence the sensitivity of the measurement of magnetic fields.

[0091] The number of devices 30 to be placed around the cable 32 and the distance between each device 30 are of course to be defined according to the type of cable 32 considered.

[0092] The invention can be applied to many types of cables, such as cables used in buildings, which are designed for voltages generally less than 1000 V, and distribution cables, which are designed for voltages generally equal to or greater than 1000 V.

Claims

Claims

1. Method for measuring the current intensity in an electric cable comprising N conductors, N being an integer greater than or equal to 2, characterized in that it consists of simultaneously measuring the current intensity in each of the N conductors by carrying out steps consisting of: - placing (E1) a set of magnetic field sensors around said cable, in at least one location along the length of said cable, said set of sensors comprising k sets of N sensors, k being an integer greater than or equal to 2, the N xk sensors of said set being distributed over a circle (Ts) and the N sensors having between them an angular offset less than or equal to 2TT / N; - calculate (E4) a plurality of inverse matrices M -1each corresponding to a different position of said set of sensors relative to said cable, each position of said set of sensors relative to said cable being defined, by assimilating the conductors and the sensors to points and the N conductors being located on a circle (Te), by: - the angle between a conductor and the nearest sensor among the N xk sensors of said set, said angle being defined relative to the center of the circle (Ts) on which the sensors are located; - the Cartesian coordinates (x e xc,yexc) from the center of the circle (Ts) on which the sensors are located, in a Cartesian frame having as its origin the center of the circle (Te) on which the conductors are located and - the radius (r) of the circle (Te) on which the conductors are located, each inverse matrix M -1 being calculated following steps (E2, E3) consisting of: - measure (E2) simultaneously, for each of the N conductors, at least one component of the magnetic field produced by the current flowing in said conductor, by means of said set of N xk magnetic field sensors; and - for each of the N conductors, determine (E3) said angle between this conductor and the nearest magnetic field sensor, the intensities of the currents in said conductors being linked to the magnetic field components measured by the relation B = pMI where B is the matrix of said magnetic field components, I is the matrix of said current intensities, M is a matrix comprising a plurality of proportionality coefficients depending on said angles between said conductors and said magnetic field sensors and p is a predetermined coefficient; - following said step (E4) of calculating said plurality of inverse matrices M' 1, deduce (E5), for each inverse matrix M' 1 , the values ​​of said current intensities I = (po / 2n).M' 1 .B, where po is an equivalent magnetic permeability which takes into account the presence of insulating materials in said cable; and - selecting (E6), from said plurality of inverse matrices M -1 calculated in calculation step (E4), the inverse matrix which corresponds to the minimum value of the difference between the matrices of the current intensities obtained in deduction step (E5) for each position of said set of sensors relative to the cable, the current intensity in each of the N conductors of said cable being the value obtained via the inverse matrix calculated in calculation step (E4) and selected in selection step (E6).

2. Method according to claim 1, characterized in that the measuring step (E2) consists of simultaneously measuring, for each of said conductors, the tangential component and / or the radial component of the magnetic field produced by the current flowing in said conductor, by means of said set of N xk magnetic field sensors.

3. Method according to claim 1 or 2, characterized in that the N sensors have between them an angular offset of 2TT / N.

4. Method according to claim 1, 2 or 3, characterized in that the k sets of sensors have between them an angular offset of 2n7(kx N).

5. Device (30) for measuring the current intensity in an electric cable (32) comprising N conductors (34), N being an integer greater than or equal to 2, characterized in that it comprises: said set of N xk magnetic field sensors (36), k being an integer greater than or equal to 2; a processing means (38) adapted to receive the values ​​of said components of the magnetic field and applying the steps (E3, E4, E5, E6) of determining the angle, calculating inverse matrices, deducing values ​​of the current intensities and selection included in a method according to any one of the preceding claims.

6. Device (30) according to claim 5, characterized in that it further comprises a housing (31) containing said set of N xk magnetic field sensors (36).

7. Device (30) according to claim 6, characterized in that said housing (31) is surrounded by electromagnetic shielding.

8. Device (30) according to claim 6 or 7, characterized in that said housing (31) has a section formed of two half-rings (311, 312), adapted to the positioning of said device (30) around said cable (32).

9. Device (30) according to any one of claims 5 to 8, characterized in that it further comprises at least one additional magnetic field sensor (37) adapted to measure the Earth's magnetic field.

10. Device (30) according to claim 9 taken attached to any one of claims 6 to 8, characterized in that said at least one additional sensor (37) is arranged inside said housing and / or outside said housing (31).

11. An electrical cable arrangement comprising an electrical cable (32) comprising N conductors (34), N being an integer greater than or equal to 2, characterized in that it further comprises at least one device (30) according to any one of claims 5 to 10 placed around said cable (32).

12. An electrical cable arrangement according to claim 11, characterized in that it comprises a plurality of devices (30) according to any one of claims 5 to 10, placed around said cable (32) at predetermined intervals from each other.

Images