METHOD AND DEVICE FOR SIMULTANEOUSLY MEASURING THE CURRENT INTENSITY IN EACH PHASE OF A POLYPHASE ELECTRICAL CABLE

Abstract

To simultaneously measure the current intensity in the N conductors of a cable, k sets of N magnetic sensors are placed around the cable (E1) with an angular offset between the sensors; a plurality of inverse matrices corresponding to different positions of the sensors relative to the cable are calculated (E4), each inverse matrix M-1 being calculated after measuring (E2), using the N xk sensors, the magnetic field produced by the current flowing in each conductor and determining (E3) the angle between each conductor and the nearest sensor; from this, the values ​​of the current intensity I = (µ0 / 2π)M-1B, where B is the magnetic field matrix and µ0 is a magnetic permeability, are deduced (E5); and the inverse matrix corresponding to the minimum of the difference between the current intensity matrices obtained in step (E5) of deduction is selected (E6). Figure for the abbreviation: Fig. 1

Description

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

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

[0002] The invention relates to the field of electrical cables intended for the transport of energy and / or the transmission of data. It is particularly applicable 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 inaccurate results.

[0005] There is no practical technical solution on the market for measuring simultaneously, quickly and accurately, the current intensity in all the conductors of a polyphase cable.

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

[0007] To this end, the present invention proposes a method for measuring the current intensity in an electrical 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 performing steps consisting of: - place a set of magnetic field sensors around the cable, in at least 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 xk sensors of this set being distributed over a circle and the N sensors having an angular offset between them less than or equal to 2ir / N; - calculate a plurality of inverse matrices M1, each corresponding to a different position of the sensor set relative to the cable, each position of the sensor set relative to the cable being defined, by approximating the conductors and sensors as 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 in the aforementioned set, this angle being defined with respect to the center of the circle on where are the sensors located? - the Cartesian coordinates of the center of the circle on which the sensors are located, in a Cartesian coordinate system whose origin is 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 M1 being calculated following the steps of: - simultaneously measuring, for each of the N conductors, at least one component of the magnetic field produced by the current flowing in the conductor, using 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 current intensities in the conductors being related 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 current intensities, 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 M1, deduce, for each inverse matrix M1, the values ​​of the current intensities I = (po / 2ir).M1.B, where po is an equivalent magnetic permeability that takes into account the presence of insulating materials in the cable; and - to select, from among the plurality of inverse matrices M1 calculated in the aforementioned calculation step, the inverse matrix that corresponds to the minimum value of the difference between the current intensity matrices obtained in the deduction step for each position of the sensor assembly 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 precise results, without having to remove the cable sheath. Furthermore, the installation of the magnetic field sensors around the cables is easy and does not cause any damage, marking, or deformation to the cables.Furthermore, since the position of the magnetic field sensors relative to the cable conductors is unknown, accounting for the angular offset between the sensors and conductors increases the accuracy of the obtained intensity values. Moreover, there is no need to store or access a matrix library, as the plurality of inverse matrices is not constructed prior to the execution of the process, but is calculated each time the process is implemented.

[0009] In addition, 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 accuracy in the measurement of the current intensities flowing in each of the N conductors of the electrical cable.

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

[0011] In a particular embodiment, the measurement 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 on the intensity values ​​obtained, that is to say to further increase the precision of these values.

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

[0014] This allows for a particularly high resolution in intensity measurements, which guarantees high measurement accuracy.

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

[0016] For the same purpose as indicated above, the present invention also proposes a device for measuring the current intensity in an electrical 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 current intensities and selection included in a process as briefly described 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 helps to prevent the penetration of electromagnetic disturbances due, for example, to the permanent Earth's magnetic field and to possible sources of electromagnetic field located near the cable and the sensors.

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

[0022] This configuration allows for quick 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 thus be subtracted when processing the magnetic field values ​​collected by the sensors.

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

[0026] Still with the same purpose as indicated above, the present invention also proposes an arrangement of electrical cable comprising an electrical cable having 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 such as succinctly described above placed around the cable.

[0027] In a particular embodiment, the electrical cable arrangement comprises a plurality of devices such as succinctly 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] The other special 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 become apparent from the following detailed description of particular embodiments, given by way of non-limiting examples, with reference to the accompanying drawings, in which:

[0031] [Fig-1] is a flowchart illustrating steps in a process conforming 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 The electrical cable in question has five conductors.

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

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

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

[0036] The present invention considers a polyphase, or multi-conductor, cable, for alternating or direct current. 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, given that a polyphase cable has several current densities 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 components of the magnetic field by determining an inverse matrix, in order to obtain the current intensities from the N current sources.

[0039] Thus, as shown in the flowchart of [Fig.1], the method, according to the invention, of measuring the current intensity in an electrical cable comprising N conductors, consists of simultaneously measuring the current intensity in each of the N conductors, as detailed below.

[0040] A first step El 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, that is to say K sets of magnetic field sensors, each comprising N magnetic field sensors.

[0041] By way of 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 over a circle Ts, of radius R, as illustrated in [Fig.5].

[0043] There may exist an angular offset between the sensors of each set of N sensors, In other words, two sets of sensors may not be positioned in the same way relative to the cable. This allows for multiple measurements, thereby increasing the accuracy of the current values ​​obtained at the end of the execution of all the steps of the process according to the present invention. In this case, the N sensors have an angular offset between them of between 0 and 2ir / N, that is to say, this angular offset is less than or equal to 2ir / N.

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

[0045] Advantageously, the angular offset between each set of N sensors is 2ir / (k x N).

[0046] Step 11 may, for example, consist of attaching one or more devices according to the invention around the cable, each device containing all or part of the aforementioned sensor assembly. The device according to the invention is described later with reference to Figures 3 and 4.

[0047] During the installation of one or more devices according to the invention in step 11, no movement is required of the device(s), the cable, or the device(s) relative to the cable or vice versa, whether translational, rotational, or any other type of movement. Furthermore, there are no constraints regarding the knowledge or application of the current intensity values ​​flowing in the cable conductors.

[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 that conductor.

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

[0050] In a particular embodiment, the magnetic field sensor assembly 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] Next, in step E3, for each conductor, the angle α between that conductor and the nearest magnetic field sensor among the N xk sensors in the magnetic field sensor array is determined. The angle α is defined with respect to the center of the circle Ts on which the sensors are located, by treating the conductors and sensors as points. As mentioned above, the sensors are located on a circle Ts. Furthermore, the conductors are located on a circle Te. Indeed, for simplicity, it is assumed that each conductor has an infinitesimally small cross-section and that the magnetic field detected by each sensor is localized to a point corresponding to the location of the sensor.

[0053] Figures 2 and 5 schematically illustrate, by way of non-limiting example, a circular cross-section cable comprising five conductors regularly distributed within the cable, which are considered as five points Cl to C5 equidistant from each other on the circumference of a circle Te. Only the magnetic field sensor closest to conductor Cl has been shown and is symbolized by point A in [Fig. 2] and by point Si in [Fig. 5]. The radius of the circle Te is denoted by r, the distance between conductor Ci and sensor A is denoted by di in [Fig. 2] and the corresponding distance between conductor Ci and sensor Si is denoted by dij in [Fig. 5], the line segment connecting sensor A and the center of circle Te is denoted by d\ in [Fig. 2], the angle at point A between the line segment d\ and the line segment connecting conductor Cl and point A is denoted by [3 in [Fig. 5].2] and the same angle is designated by ôjj on [Fig.5]. On [Fig.2], the magnetic field captured by sensor A is represented by the vector Bb which is orthogonal to the line segment connecting conductor Cl and point A and on [Fig.5], the same magnetic field is represented by the vector Btot, whose tangential component is represented by the vector BT and the radial component is represented by the vector Bp.

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

[0055] [Math.l] B A = Y > B t = Y, ..B im • cos( / l) = Y 7 ' cos (Arcsinij ) • / • / 1 i ^i=i un i / a,- \ \. dj / / a

[0056] where: Bim is the component of the magnetic field coming from the ith conductor captured by the mth sensor; the angles a; and [3; are defined for the i-th conductor in a similar way to the angles a and [3 defined above, respectively; di denotes the distance between the i-th conductor and the nearest sensor; po is an equivalent magnetic permeability that takes into account the presence of insulating materials in the cable; r is, as defined above, the radius of the circle Te; and Iim is the value of the intensity of the current flowing in the th conductor and deduced from the magnetic field measurement carried out by the mth sensor.

[0057] Thus, the current intensities in the conductors are related to the measured magnetic field components by the relation B = pMI, where B is the matrix of magnetic field components measured in all conductors by all sensors, and I is the matrix of current intensities flowing in all the 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.

[0058] It follows that I = (po / 2ir).M *.B, where M 1 is the inverse matrix of M.

[0059] Thus, as shown in [Fig. 1], following the measurement steps E2 and determination steps E3 Calculation of the angle a between each conductor and the nearest sensor, we carry out a step E4 consisting of calculating a plurality of inverse matrices M 1 each corresponding to a different position of the set of sensors relative to the cable.

[0060] Each position of the sensor assembly relative to the cable is defined by: - the angle between a conductor and the nearest sensor among the N xk sensors in the sensor set, this angle being defined with respect to the center of the circle Ts on which the sensors are located; - the Cartesian coordinates (xexc, yexc), shown in [Fig. 5], of the center of the circle Ts on which the sensors are located, in a Cartesian coordinate system whose origin is the center of the circle Te on which the conductors are located (the center of the circle Te therefore having (0, 0) Cartesian coordinates, as shown in [Fig. 5]); and - the radius r of the circle Te on which the conductors are located.

[0061] Calculating the plurality of inverse matrices M1 in step E4 allows us to deduce, in the following step E5, for each inverse matrix M1, the values ​​of the current intensities I = (po / 2ir).MTB in all the conductors of the cable.

[0062] Then during a step E6, the matrices giving values ​​of the current intensities I obtained in the deduction step E5 are compared with each other and the inverse matrix M1 calculated in the calculation step E4 is selected from among the plurality of inverse matrices M1, which corresponds to the minimum value of the difference between the matrices of the current intensities I obtained in the calculation step E5.

[0063] 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 step E4 of calculation and selected in step E6 of selection.

[0064] By way of 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 allowing the intensities of the currents in the conductors by the first set of sensors A, B, C, D and E to be deduced is as follows:

[0065] [Math.2] 1 d. 1 Æ, ■cos (fl 1 cos(fl4) 1 d5 -1 tni 1 ■cos^) 1 -A cos( 1 'h 'cosW 1 ■cos(fl3) 1 A BA\ Bb 1 1 â5 ot( 1 ■ COS^fl} 1 A cos(fl^ ) i d. ■cos(p3) Bc 1 ot( / Q 1 A 1 ^5 ■ cos (fl 1 ■cos(fl^ 1 d. cos{ fl^ Bd 1 A COS ( / 3^ 1 ■cos{p3) 1 A ■ cos ( / 3 J 1 rf5 ■cos{^) 1 cos^) L. 1

[0066] where 1;, i = 1, ---,5 denotes the intensity of the current flowing in the th conductor and BA, Bb, Bc, Bd and Be denote the components of the magnetic field respectively measured by the five sensors of the first set of sensors.

[0067] The equivalent magnetic permeability po is a macroscopic permeability, which makes the calculation simpler than if one considered the local magnetic permeability.

[0068] The second set of 5 sensors A', B', C', D' and E' is positioned on the same circle Ts The first set of 5 sensors A, B, C, D, and E, and the 5 sensors in each subsequent set, are angularly offset from each other by an angle less than or equal to 2ir / 5. Furthermore, and as a non-limiting example, the angular offset between these two sets of sensors can be ir / 5. This allows for very good resolution in intensity measurement and therefore high measurement accuracy.

[0069] For the second set of sensors A', B', C', D' and E', at step E4, another matrix M 1 is calculated similar to that given above in the detail of the relation 1= (po / 2ir).M LB.

[0070] If we denote I as the intensity matrix deduced from the first set of sensors A, B, C, D, and E, and F as the intensity matrix deduced from the second set of sensors A', B', C', D', and E', step E6 comprises an operation consisting of comparing I and I'. The parameters corresponding to the installation of the current intensity measurement device in the cable under consideration will be those that give the minimum difference between I and I'.

[0071] 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:

[0072] [Math.3]

[0073] where h denotes the intensity of the current flowing in the th conductor.

[0074] There are various methods of mathematical convergence known in themselves to maximize F, such as the Levenberg-Marquardt algorithm (also called the LM algorithm) or the Nelder-Mead method.

[0075] As shown in [Fig. 3], a device 30 according to the present invention, of The measurement of current intensity in an electrical cable 32 comprising N conductors 34, where N is an integer greater than or equal to 2, includes the aforementioned set of N xk magnetic field sensors 36, where k is an integer greater than or equal to 2. In the non-limiting example shown, the set of sensors 36 consists of two sets of five sensors each, one set being shown with solid lines and the other set with dashed lines.

[0076] The device 30 also includes a processing means 38 adapted to receive the values ​​of the magnetic field components measured by the sensor set 36 and to apply the steps E3 of angle determination, E4 of inverse matrix calculation, E5 of deduction of current intensity values ​​and E6 of selection included in the process described above, to deduce a value of the current intensity flowing in each of the conductors 34 with increased accuracy.

[0077] The processing means 38 can be located either within the device 30 or remotely from it, in which case a communication means is provided to transmit the measured magnetic field component values ​​from the sensors 36 to the processing means 38. When located remotely from the device 30, the processing means 38 can be located in a laptop or desktop computer, a tablet, a smartphone or other mobile communication device, or even be located in the cloud.

[0078] 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 within any enclosure.

[0079] In the particular embodiment illustrated, the housing 31 has a section formed of 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 through which the cable 32 passes. In the particular embodiment illustrated, the cable 32 has a circular cross-section and the opening formed by the two half-rings 311 and 312 is also circular and of a diameter slightly greater than that of the cross-section of the cable.

[0080] 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 secured to each other, for example, by means of screws or nuts or other preferably removable fastening means.

[0081] Optionally, the housing 31 can also be surrounded by electromagnetic shielding to prevent interference with the sensors from any surrounding sources of electromagnetic waves as well as from the Earth's permanent magnetic field. This shielding can be made, for example, of a specific steel.

[0082] Whether such shielding is present or not, the device 30 can also be equipped with a or several additional magnetic field sensors 37 adapted to measure, in particular, the Earth's magnetic field, in order to subtract its value when processing the values ​​of the magnetic field components measured by the magnetic field sensors 36. The additional sensor(s) 37 can be arranged inside and / or outside the housing 31, or directly around the cable when there is no housing.

[0083] Thus, an electrical cable arrangement according to the present invention comprises the cable 32 having N conductors 34, N being the integer greater than or equal to 2 mentioned above and at least one device 30 placed around the cable 32.

[0084] As shown in the particular embodiment of [Fig.4], the electrical cable arrangement can include a plurality of devices 30, placed around the cable 32 at predetermined intervals from each other.

[0085] The processing means 38 may be unique and common to all 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 optionally be provided.

[0086] In the particular embodiment illustrated, the devices 30 are all identical, each includes two sets of five magnetic field sensors 36 and are arranged at regular intervals along the cable 32.

[0087] Such a configuration makes it possible to guarantee a high quality measurement of current intensities including in the case where the conductors 34 are twisted, for example due to manufacturing conditions and / or specific constraints, which could affect the sensitivity of the measurement of magnetic fields.

[0088] 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.

[0089] The invention can be applied to many types of cables, such as cables used in buildings, which are designed for voltages generally below 1000 V, and distribution cables, which are designed for voltages generally equal to or greater than 1000 V.

Claims

Demands

1. A method for measuring the current intensity in an electrical 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 performing steps consisting of: - place (El) a set of magnetic field sensors around said cable, in at least one location on 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 an angular offset between them less than or equal to 2ir / N; - calculate (E4) a plurality of inverse matrices M 1 each corresponding to a different position of said sensor set relative to said cable, each position of said sensor set relative to said cable being defined, by assimilating the conductors and 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 with respect to the center of the circle (Ts) on which the sensors are located; - the Cartesian coordinates (xexc, yexc) of the center of the circle (Ts) on which the sensors are located, in a Cartesian coordinate system whose origin is 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 M1 being calculated following steps (E2, E3) consisting of: - to 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) the angle between this conductor and the nearest magnetic field sensor, the current intensities in said conductors being related to the components of the magnetic field measured by the relation B = pMI where B is the matrix of said components of the magnetic field, 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 calculation of said plurality of inverse matrices M1, deduce (E5), for each inverse matrix M1, the values ​​of said current intensities I = (po / 2ir).M *.B, where po is an equivalent magnetic permeability which takes into account the presence of insulating materials in said cable; and - select (E6), from said plurality of inverse matrices M1 calculated in step (E4) of calculation, the inverse matrix which corresponds to the minimum value of the difference between the matrices of current intensities obtained in step (E5) of deduction for each position of said set of sensors with respect to the cable, the current intensity in each of the N conductors of said cable being the value obtained by means of the inverse matrix calculated in step (E4) of calculation and selected in step (E6) of selection.

2. Method according to claim 1, characterized in that the measurement 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 an angular offset of 2ir / N between them.

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

5. Device (30) for measuring the current intensity in an electrical 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 magnetic field components and to apply the steps (E3, E4, E5, E6) of angle determination, calculation of inverse matrices, deduction of current intensity values ​​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 in relation to any one of claims 6 to 8, characterized in that said at least one additional sensor (37) is disposed inside said housing and / or outside said housing (31).

11. 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. 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.

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