Device for measuring the intensity of an electric current

Abstract

Device comprising a measurement module (15, 151, 152) including: separate inductive sensors (2a, 2b, 2c) having different measurement ranges and / or a multi-range inductive sensor (20) having different measurement ranges, to be arranged around a conductor (4), a multiplexer (5) for receiving an analog measurement signal from each inductive sensor and / or an input channel for receiving the analog measurement signals from the multi-range inductive sensor, the multiplexer delivering at output only one of said analog measurement signals, a converter (6) converting the analog measurement signal into a digital signal, the device including a microcontroller (7) for selecting the optimal measurement signal which has the maximum measurement accuracy.

Description

Title of the invention: Device for measuring the intensity of an electric current technical field

[0001] The present invention relates to a method and a device for measuring the intensity of an electric current flowing in a conductor.

[0002] The invention relates to the field of electrical cables for the transmission of energy. In particular, it can be implemented in the field of optimizing the distribution of electrical energy in buildings.

[0003] Currently, the current intensity is most often measured using an ammeter clamp in each conductor of an installation.

[0004] However, this measurement is time-consuming and generally provides a result whose accuracy depends on the current range that the clamp meter is capable of measuring and the current flowing in the conductor. This measurement accuracy can therefore vary with large changes in current intensity.

[0005] In addition, the measurement generally requires the movement of an operator to perform the measurement in situ.

[0006] There is therefore a need to measure precisely and easily the intensity of an electric current flowing in a conductor over time, and not only at a single point. Furthermore, there is a need to simultaneously measure the intensities of the currents flowing in several conductors of an electrical cable network. Summary of the invention

[0007] The invention relates to a device for measuring the intensity of the electric current flowing in at least one conductor, the device comprising a measuring module including: separate inductive sensors with different current measurement ranges and / or a multi-range inductive sensor with different current measurement ranges, to be placed around a conductor, a multiplexer comprising input channels each connected to one of the inductive sensors in order to receive an analog measurement signal generated by said inductive sensor when a current passes through the conductor and / or an input channel to receive the analog measurement signals acquired according to the different measurement ranges of the multi-range inductive sensor when a current passes through the conductor, the multiplexer being configured to deliver at output only one of said analog measurement signals, an analog-to-digital converter to convert the analog measurement signal supplied at the output of the multiplexer into a digital signal, the device further includes a microcontroller configured to select the optimal measurement signal from the measurement module by: - controlling the multiplexer to successively transmit each of the analog measurement signals received at the multiplexer's input to the analog-to-digital converter, - analyzing each of the corresponding digital signals transmitted by the analog-to-digital converter in order to determine the optimal analog measurement signal that exhibits the maximum measurement accuracy, and - controlling the multiplexer to select the optimal analog measurement signal.

[0008] The device according to the invention advantageously allows for the precise measurement of the intensity of the current flowing in the conductor, by choosing the inductive sensor presenting the intensity measurement range most suited to the intensity of the current flowing at a given instant in the conductor.

[0009] Preferably, the device includes a radio frequency communication module for transmitting the optimal analog measurement signal and / or the corresponding digital signal to a remote device. Advantageously, as will be illustrated later, precise remote monitoring of the current intensity flowing in a conductor can be carried out, particularly without requiring an operator to travel. The radio frequency communication module may include a radio frequency wave transmitter, for example, equipped with a Wi-Fi® or Bluetooth® chip.

[0010] Preferably, the microcontroller is configured to calculate, for each of the analog measurement signals and over a measurement time interval, the difference A between the maximum and minimum values ​​of the corresponding digital signal, the optimal analog measurement signal being the unsaturated digital signal exhibiting the greatest difference A. The microcontroller is thus able to select the inductive sensor providing the most accurate current measurement. Furthermore, the corresponding optimal analog measurement signal is unsaturated.

[0011] The duration of a measurement time interval can be the minimum duration of a frequency cycle of the electrical network.

[0012] The microcontroller is preferably configured to calculate the deviation A further without saturation of the analog or digital signals over different measurement time intervals and, for each of the measurement time intervals, to control the multiplexer so as to select the corresponding optimal analog measurement signal. In this way, the device is adapted to modify the choice of sensor An inductive sensor provides the most accurate measurement during a significant change in current intensity. For example, when the current intensity increases beyond the upper limit of the measurement range of one of the inductive sensors, the microcontroller can instruct the multiplexer to select another inductive sensor with a more accurate measurement range in relation to the change in intensity.

[0013] The deviation A is a precision indicator that, in particular, determines the number of bits on which the difference between the minimum and maximum values ​​of the analog measurement signal from each inductive sensor can be encoded. The larger the deviation A, the greater the encoding precision of the difference between the minimum and maximum values ​​of each signal on A bits.

[0014] When the analog measurement signal transmitted by the multiplexer is periodic: - the measurement time interval over which the measurement is performed may be equal to one or more periods, and / or - the maximum and minimum values ​​of the signal can be the maximum and minimum values ​​of the peak-to-peak signal amplitude.

[0015] When the analog measurement signal transmitted by the multiplexer is aperiodic, the maximum and minimum values ​​of the signal are preferably the maximum and minimum values ​​respectively of the signal amplitude measured during the time interval.

[0016] The multiplexer may have several input channels, for example between 2 and 10 input channels, or even between 2 and 8 input channels, for example 3 input channels.

[0017] The multiplexer may have as many input channels as there are inductive sensors, each inductive sensor being electrically connected to one of the corresponding input channels of the multiplexer. The multiplexer may have an analog output for delivering one of said analog measurement signals.

[0018] The analog output signal of the multiplexer can be electrically connected to the analog-to-digital converter.

[0019] The analog-to-digital converter can be configured to convert the analog signal into a digital signal coded on at least 4 bits, or even on at least 8 bits, or even on at least 10 bits, preferably on at least 12 bits, in particular 16 bits.

[0020] The microcontroller input can be electrically connected to the output of the analog-to-digital converter, in particular by wire, to receive as input the digital signal from the analog-to-digital converter.

[0021] The separate inductive sensors can each be single-range. A single-range inductive sensor is suitable for measuring the intensity of an electric current over a single intensity measurement range.

[0022] Single-range inductive sensors have different current intensity measurement ranges. For example, a first inductive sensor has a measurement range between 0 and 10 A, a second inductive sensor has a measurement range between 0 and 100 A, and a third inductive sensor has a measurement range between 0 and 1000 A.

[0023] A multi-range inductive sensor is suitable for measuring current intensity by adapting the measurement range. For example, a multi-range sensor can measure current intensity over a measurement range of 0 to 10 A, over a measurement range of 0 to 100 A, and over a measurement range of 0 to 100 A.

[0024] At least one, in particular each of the inductive sensors can be chosen from a Rogowski sensor, a Hall effect sensor and a current transformer. Preferably, at least one, preferably each of the inductive sensors can be a Rogowski sensor which has the advantage of easy installation around the conductor.

[0025] The multiplexer and the measuring module(s) can be mounted on a support. In particular, they can be mounted on a plastic card and connected to each other by a printed electrical circuit. The support, for example the plastic card, can be flexible and conformable, for example to fit the shape of the conductor.

[0026] Alternatively, the device may comprise a rigid housing in which the multiplexer and the measuring module(s) are housed. The housing may further comprise the inductive sensors. Alternatively, the inductive sensors may be located outside the housing. The housing may, in particular, have a cross-section formed by two half-rings, adapted for positioning the device around the conductor in order to encircle it.

[0027] Each of the inductive sensors can be applied to an electrical cable comprising a conductor, the current flowing in said conductor.

[0028] Furthermore, the measuring device can be adapted to measure the intensity of the current flowing in different conductors, for example in an electrical cable.

[0029] In particular, the device may include several measurement modules for measuring the current intensity in different conductors, the inductive sensor(s) of each measurement module being configured to be arranged around one of the conductors, the microcontroller being configured to receive the digital signals from each measurement module, and to select, for each measurement module, the corresponding optimal measurement signal.

[0030] For example, in a three-phase current cable, the device may include three measuring modules to measure the current intensity of each phase flowing in the three conductors of the cable.

[0031] Preferably, the radio frequency communication module is configured to teletransmit the optimal analog measurement signal and / or the corresponding digital signal from each measurement module to a remote device.

[0032] The invention also relates to a method for measuring the intensity of an electric current, the method comprising: - the provision of a device according to the invention and a conductor around which the inductive sensors are arranged, an electric current flowing in the conductor, - the reception by the multiplexer of the analog measurement signals emitted by the corresponding inductive sensors, - the control of the multiplexer by the microcontroller to transmit successively to the analog-to-digital converter each of the analog measurement signals received at the input of the multiplexer, - the analysis of each of the corresponding digital signals by the microcontroller in order to determine the optimal analog measurement signal that exhibits the maximum measurement accuracy, and - the multiplexer control to select the optimal analog measurement signal.

[0033] The conductor can be a conductor of a single-phase or polyphase electrical cable.

[0034] The current flowing in the conductor can be direct or alternating.

[0035] The invention further relates to an installation comprising: - several measuring devices, each according to the invention, - a network of electrical cables, in particular electrically connected to each other, each comprising a conductor around which the inductive sensors of one of the devices are arranged, and - a monitoring module configured to receive output signals transmitted by each of the devices.

[0036] The monitoring module may include a radio frequency receiver to receive the corresponding digital signals transmitted remotely by the radio frequency communication module, for example according to a Bluetooth, Wifi communication protocol.

[0037] The monitoring module thus collects remotely the measurements of the current intensities of each conductor, in particular in real time, for example in order to be alerted to a potential imbalance of the current intensities flowing in the installation.

[0038] The monitoring module can be configured to issue an alert, in order to intervene on the installation when the distribution of the electrical current intensity in the installation is unbalanced between the conductors or when a malfunction of at least one of the devices is observed.

[0039] The installation can be chosen from a collective residential building, an office building, a sports facility, an industrial installation, for example a factory, a computer data storage and / or processing center, an electrical power distribution network, for example underground or overhead.

[0040] At least two of the devices can be spaced more than 1 m apart, or even more than 10 m apart, or even more than 100 m apart.

[0041] The installation may include more than 10 devices, or even more than 100 devices. Brief description of the drawings

[0042] The invention will be better understood upon reading the detailed description that follows, the non-limiting examples of its implementation, and upon examination of the accompanying drawing, on which: [Fig. 1], [Fig. 2] and [Fig. 3] are schematic and partial views of different examples of the device according to the invention, and [Fig.4] [Fig.4] illustrates an example of installation according to the invention. Detailed description

[0043] Figure 1 illustrates an example of a device 1 according to the invention. The device comprises three inductive current sensors 2a, 2b, and 2c. This number of sensors is not limiting, provided that the device comprises at least two. Each inductive sensor has a Rogowski coil that encircles the cable 3. In the illustrated example, the cable 3 is single-phase and has a single conductor 4 through which an alternating or direct current flows.

[0044] The inductive sensors 2a, 2b and 2c have different current intensity measurement ranges.

[0045] A multiplexer 5 is electrically connected to each of the sensors 2a, 2b and 2c. It has three input channels Ea, Eb and Ec. Each input channel Ea, Eb and Ec is electrically connected to the output of each of the sensors 2a, 2b and 2c respectively so that said multiplexer 5 receives as input the analog measurement signals of the current, flowing in the conductor 4 of the cable 3, generated by each inductive current sensor.

[0046] The multiplexer has a single output Sm electrically connected to the analog-to-digital converter 6. The multiplexer, the analog converter, and the inductive sensors together define a measurement module 15. The multiplexer 5 is also controlled by a microcontroller 7 in order to successively transmit to the analog-to-digital converter the analog measurement signals provided by each inductive current sensor. The analog-to-digital converter then successively converts the analog measurement signals coming from the multiplexer. It outputs a digital signal, for example coded on a range from 0 to 12 bits, and transmits it to the microcontroller 7.

[0047] Initially, the microcontroller 7, for example, commands the multiplexer to transmit the analog measurement signal emitted by the inductive sensor 2a to the analog-to-digital converter 6. Then, the microcontroller 7 commands the multiplexer to transmit to the analog-to-digital converter 6 the analog measurement signal from another of the inductive sensors, for example, sensor 2b. The microcontroller thus successively analyzes each of the corresponding digital signals coming from the analog-to-digital converter 6. From the minimum and maximum values ​​of each digital measurement signal, the microcontroller determines the deviation A corresponding to the difference between the minimum and maximum values ​​of said digital signal.

[0048] The microcontroller 7 thus commands the multiplexer to select the inductive current sensor corresponding to the maximum deviation A, so that the most accurate measurement is carried out with this sensor.

[0049] The optimal analog measurement signal and / or the corresponding digital signal can then be transmitted by a radio frequency communication module 8 to a remote monitoring module 9.

[0050] Table 1 shows, in an illustrative and schematic way, the calculations of the deviations A of the digital signals corresponding to measurements made by the inductive sensors 2a, 2b and 2c of the device illustrated in [Fig.1].

[0051] [Tables 1] Sensor 2a 2b 2c Current measurement range (A) 0 to 10 0 to 100 0 to 1000 Analog signal voltage range (V) ± 1 Current flowing in the conductor (A) 50 Measured analog signal voltage (V) ± 1 ±0.5 ±0.05 Deviation A (12-bit encoding) saturation 2048 205

[0052] In this example, the signal of an alternating current of intensity I equal to 50 A is converted into an analog signal of ± 1 V by the sensors, i.e. varying temporally between - IV and IV.

[0053] The inductive sensors 2a, 2b and 2c have different current measurement ranges. Sensor 3a has a measurement range from 0 to 10 A, sensor 3b a measurement range from 0 to 100 A and sensor 3c a measurement range from 0 to 1000 A.

[0054] The analog measurement signal voltage emitted by each inductive sensor is between -1 and 1 V. For the first sensor 2a, capable of measuring a current between 0 and 10 A, the analog measurement signal voltage is saturated and capped by the maximum value of the measurement range, i.e., 10 A. The analog signal is therefore also saturated and capped at IV. For the second and third inductive sensors 2b and 3b, it varies between -0.5 V and 0.5 V and between -0.05 V and 0.05 V respectively.

[0055] The analog converter 6 encodes the analog measurement signal, for example, on 12 bits. The digital signal at the output of the converter for each inductive sensor will therefore be equal to the integer closest to the result of multiplying the voltage value of the analog signal by 212. Saturation of the digital signal is reached for the maximum value that can be encoded, i.e. in the example 212 (4096) bits.

[0056] The microcontroller 7 then determines the optimal measurement range it receives from the analog-to-digital converter 6. To do this, the microcontroller rejects measurement ranges exhibiting saturation (digital signal value equal to the maximum number of the converter) and selects the measurement range exhibiting the maximum deviation A among the unsaturated digital signals.

[0057] As observed in Table 1, the unsaturated digital signal exhibiting the maximum deviation A (2048) therefore corresponds to the optimal analog measurement signal generated by the inductive current sensor 2b. The digital signal from the inductive current sensor 2a has a deviation equal to the maximum digital encoding range value (4096) and is therefore saturated. It is thus excluded by the microcontroller.

[0058] Figure 2 illustrates another example of a device according to the invention. It differs from the one illustrated in Figure 1 in that the measuring module 15 comprises a multi-range inductive sensor 20 instead of the separate inductive sensors 2a, 2b, and 2c. The multi-range inductive sensor measures the intensity of the electric current by successively selecting the different measurement ranges and transmits each analog measurement signal according to a corresponding range to the multiplexer 5, which at the output selects one of said analog measurement signals which it transmits to the analog-to-digital converter 6.

[0059] Fig. 3 illustrates another example of a device according to the invention.

[0060] Device 1 comprises several measuring modules 151 and 152. In the illustrated example, two measuring modules are shown, but this number of measuring modules is not limiting and can be increased, in particular with regard to the number of conductors for which the measurement of the current intensity is desired.

[0061] The inductive sensors of each measuring module are arranged around conductors 3a and 3b of an electrical cable 4. Each measuring module 151, 152 acquires analog current measurement signals flowing in the corresponding conductor 3a, 3b respectively. Once digitized by the analog-to-digital converters of each of the measuring modules 151, 152, the corresponding digital signals are transmitted to the microcontroller 7, which, by analyzing them, can control the multiplexer of the corresponding measuring module to select the optimal analog measurement signal. The optimal analog signal from measuring module 151 and the optimal analog signal from measuring module 152 can then be transmitted remotely by the microcontroller to the remote device 8.

[0062] Figure 4 represents an example of an installation 10 comprising a network of electrical cables 3 comprising one or more conductors 4. The installation includes devices 1 according to the invention, for example as illustrated in Figure 1, and one or more electrical devices 11 electrically powered by the cables 3. It further includes a monitoring module 9 which includes a radio frequency wave receiver for receiving the optimal analog measurement signal and / or the digital signal emitted by the radio frequency communication module of each of the devices 1. In this way, real-time monitoring of the current intensities flowing in the cables can be carried out, which makes it possible to modify, if necessary, the distribution of the electrical current in the installation.

[0063] The invention is not limited to the example described above. Numerous modifications can be made to the device just described, without departing from the scope of the present invention.

Claims

1. Demands Device (1) for measuring the intensity of the electric current flowing in at least one conductor, the device comprising a measuring module (15, 151, 152) comprising: separate inductive sensors (2a, 2b, 2c) having different current intensity measurement ranges and / or a multi-range inductive sensor (20) having different current intensity measurement ranges, to be arranged around a conductor (4), a multiplexer (5) having input channels (Ea, Eb, Ec) each connected to one of the inductive sensors (2a, 2b, 2c) in order to receive an analog measurement signal generated by said inductive sensor when a current passes through the conductor and / or an input channel to receive the analog measurement signals acquired according to the different measurement ranges of the multi-range inductive sensor when a current passes through the conductor, the multiplexer being configured to deliver at output only one of said analog measurement signals, an analog-to-digital converter (6) to convert the analog measurement signal supplied at the output of the multiplexer into a digital signal, the device further comprising a microcontroller (7) configured to select the optimal measurement signal from the measurement module by: - controlling the multiplexer (5) in order to successively transmit to the analog-to-digital converter (6) each of the analog measurement signals received at the input of the multiplexer, - analyzing each of the corresponding digital signals transmitted by the analog-to-digital converter (6) in order to determine the optimal analog measurement signal that exhibits the maximum measurement accuracy, and - controlling the multiplexer to select the optimal analog measurement signal, the device (1) further comprising a housing containing the inductive sensors (2a,2b,2c), the housing having a section formed of two half-rings, adapted to the positioning of the device (1) around the conductor (4) in order to encircle the latter.

2. Device according to claim 1, further comprising a radio frequency communication module (8) for teletransmitting the optimal analog measurement signal and / or the corresponding digital signal to a remote device.

3. Device according to any one of claims 1 and 2, the microcontroller (7) being configured to calculate, for each of the analog measurement signals and during a measurement time interval, the deviation A between the maximum and minimum values ​​of the corresponding digital signal, the optimal analog measurement signal corresponding to the unsaturated digital signal exhibiting the largest deviation A.

4. Device according to the preceding claim, the microcontroller (7) being configured to calculate the non-saturation deviation A of the analog or digital signals over different measurement time intervals and, for each of the measurement time intervals, to control the multiplexer (5) so as to select the corresponding optimal analog measurement signal.

5. Device according to any one of the preceding claims, each inductive sensor (2a,2b,2c) comprising a Rogowski coil.

6. A device according to any one of the preceding claims, comprising several measuring modules (151,152) for measuring the current intensity in different conductors (3a, 3b), the inductive sensor(s) (2a,2b,2c,20) of each measuring module being configured to be arranged around one of the conductors, the microcontroller being configured to receive the digital signals from each measuring module, and to select, for each measuring module, the corresponding optimal measurement signal.

7. Device according to the preceding claim taken in dependence on claim 2, the radio frequency communication module (8) being configured to teletransmit the optimal analog measurement signal and / or the corresponding digital signal from each measurement module to a remote device.

8. A method for measuring the intensity of an electric current, the method comprising: - providing a device (1) according to any one of the preceding claims and at least one conductor (4) around in which the inductive sensor(s) are arranged, an electric current flowing in the conductor, - the reception by the multiplexer (5) of the analog measurement signals emitted by the corresponding inductive sensor(s), - the control of the multiplexer (5) by the microcontroller (7) to transmit to the analog-to-digital converter (6), successively, each of the analog measurement signals received at the input of the multiplexer, - the analysis of each of the corresponding digital signals by the microcontroller (7) in order to determine the optimal analog measurement signal which has the maximum measurement accuracy, and - the control of the multiplexer to select the optimal analog measurement signal.

9. Method according to the preceding claim, the microcontroller (7) being configured to calculate, for each of the analog measurement signals and during a measurement time interval, the deviation A between the maximum and minimum values ​​of the corresponding digital signal, the optimal analog measurement signal corresponding to the unsaturated digital signal exhibiting the largest deviation A.

10. Method according to the preceding claim, the microcontroller (7) being configured to calculate the non-saturation deviation A of the analog or digital signals over different measurement time intervals and, for each of the measurement time intervals, to control the multiplexer (5) so as to select the corresponding optimal analog measurement signal.

11. A method according to any one of claims 8 to 10, the conductor (4) being a conductor of a single-phase or polyphase electrical cable (3).

12. Method according to the preceding claim, the current flowing in the conductor being direct or alternating.

13. Installation (10) comprising: - several measuring devices (1), each according to any one of claims 1 to 7, - a network of electrical cables (3), in particular electrically connected to each other, each comprising a conductor (4) around which are arranged the inductive sensors (2a, 2b, 2c) of one of the devices, and - a monitoring module (9) configured to receive output signals transmitted by each of the devices.

14. Installation according to the preceding claim, the devices further being according to claim 2 and the monitoring module (9) comprising a radio frequency receiver for receiving the corresponding digital signals teletransmitted by the radio frequency communication module.

15. Installation according to the preceding claim, selected from a collective residential building, an office building, a sports facility, an industrial installation, for example a factory, a computer data storage and / or processing center, an electrical power distribution network.

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