Device for measuring the intensity of an electric current

Abstract

Device comprising a measuring module (15, 151, 152) comprising: separate inductive sensors (2a, 2b, 2c) having different measuring ranges and / or a multi-caliber inductive sensor (20) having different measuring calibers, to be arranged around a conductor (4), a multiplexer (5) for receiving an analog measuring signal from each inductive sensor and / or an input channel for receiving the analog measuring signals from the multi-caliber inductive sensor, the multiplexer delivering as output only one of said analog measuring signals, a converter (6) converting the analog measuring signal into a digital signal, the device comprising a microcontroller (7) for selecting the optimal measuring signal which has the maximum measuring 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 belongs to the field of electric cables intended for the transport of energy. It can in particular 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 intensity range that the current clamp is capable of measuring and the intensity flowing in the conductor. This measurement accuracy can thus vary during large variations in current intensity.

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

[0006] There is therefore a need to precisely and easily measure the intensity of an electric current flowing in a conductor over time and not only punctually. There is also a need to simultaneously measure the intensities of the currents flowing in several conductors of a network of electric cables. 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 comprising: separate inductive sensors having different current intensity measurement ranges and / or a multi-caliber inductive sensor having different current intensity measurement calibers, to be arranged 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 for receiving the analog measurement signals acquired according to the different measurement calibers of the multi-caliber inductive sensor when a current passes through the conductor, the multiplexer being configured to deliver as output only one of said analog measurement signals, an analog-to-digital converter for converting the analog measurement signal supplied at the output of the multiplexer into a digital signal, the device further comprising a microcontroller configured to select the optimal measurement signal from the measurement module by: - controlling the multiplexer in order to successively transmit to the analog-digital converter 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 in order to determine the optimal analog measurement signal which exhibits the maximum measurement accuracy, and - controlling the multiplexer to select the optimal analog measurement signal.

[0008] The device according to the invention advantageously makes it possible to precisely measure the intensity of the current flowing in the conductor, by choosing the inductive sensor having the intensity measurement range most suited to the intensity of the current flowing at a given instant in the conductor.

[0009] Preferably, the device comprises a radiofrequency communication module for transmitting the optimal analog measurement signal and / or the corresponding digital signal to a remote device. Advantageously, as will be illustrated in particular below, precise and remote monitoring of the intensity of the current flowing in a conductor can be carried out, in particular without the need for an operator to move. The radiofrequency communication module may comprise a radiofrequency wave transmitter, for example equipped with a Wi-Fi® chip or a Bluetooth® chip.

[0010] Preferably, the microcontroller is configured to calculate, for each of the analog measurement signals and during a measurement time interval, the difference A between the maximum and minimum values ​​of the corresponding digital signal, the optimal analog measurement signal corresponding to the unsaturated digital signal having the largest difference A. The microcontroller is thus able to select the inductive sensor providing the most precise measurement of the current intensity. The corresponding optimal analog measurement signal is furthermore unsaturated.

[0011] The duration of a measurement time interval may 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, 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 the sensor inductive sensor providing the most accurate measurement during a significant variation 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 control the multiplexer to select another of the inductive sensors having a more accurate measurement range with regard to the variation in intensity.

[0013] The difference A is a precision indicator which makes it possible in particular to determine the number of bits on which it is possible to code the difference between the minimum and maximum values ​​of the analog measurement signal of each inductive sensor. The greater the difference A, the greater the precision of coding 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 carried out may be equal to one or more periods, and / or - the maximum and minimum values ​​of the signal can be the maximum value and the minimum value 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 amplitude of the signal measured during the time interval.

[0016] The multiplexer may comprise 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 comprise 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 comprise an analog output for delivering as output only 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 input of the microcontroller can be electrically connected to the output of the analog-digital converter, in particular by wire, to receive as input the digital signal coming from the analog-digital converter.

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

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

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

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

[0025] The multiplexer and the measurement module(s) may be arranged on a support. In particular, they may be arranged on a plastic card and connected to each other by a printed electrical circuit. The support, for example the plastic card, may be flexible and conformable, for example in order to match the shape of the conductor.

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

[0027] Each of the inductive sensors can be applied to an electric 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 an electric cable.

[0029] In particular, the device may comprise several measuring modules for measuring the current intensity in different conductors, the inductive sensor(s) 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 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 comprise three measurement modules for measuring the current intensity of each phase flowing in the three conductors of the cable.

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

[0032] The invention further 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, - 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 to the analog-digital converter, 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 in order to determine the optimal analog measurement signal which presents the maximum measurement accuracy, and - multiplexer control to select the optimal analog measurement signal.

[0033] The conductor may be a conductor of a single-phase or polyphase electric cable.

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

[0035] The invention also 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 the output signals transmitted by each of the devices.

[0036] The monitoring module may comprise a radiofrequency receiver for receiving the corresponding digital signals transmitted remotely by the radiofrequency communication module, for example according to a Bluetooth or Wifi communication protocol.

[0037] The monitoring module thus remotely collects measurements of the current intensities of each conductor, in particular in real time, for example in order to be alerted to a potential imbalance in the current intensities circulating 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 intensity of the electric current in the installation is unbalanced between the conductors or when an operating anomaly of at least one of the devices is observed.

[0039] The installation can be chosen from a collective residential building, a office building, a sports facility, an industrial facility, 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 may be spaced more than 1 m, or even more than 10 m, or even more than 100 m from each other.

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

[0042] The invention may be better understood by reading the detailed description which follows, non-limiting examples of its implementation, and by examining the attached drawing, in which: [Fig.l], [Fig.2] and [Fig.3] are schematic and partial views of different examples of devices according to the invention, and [Fig.4] [Fig.4] illustrates an example of installation according to the invention. Detailed description

[0043] [Fig.l] 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 comprises a Rogowski winding which surrounds the cable 3. In the example illustrated, the cable 3 is single-phase and comprises a single conductor 4 in 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 comprises 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 furthermore controlled by a microcontroller 7 in order to successively transmit to the analog-to-digital converter the analog measurement signals supplied 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 over a range from 0 to 12 bits, and transmits it to the microcontroller 7.

[0047] In a first step, the microcontroller 7 controls, for example, the multiplexer to transmit the analog measurement signal emitted by the inductive sensor 2a to the analog-digital converter 6. Then, the microcontroller 7 controls the multiplexer in order to transmit to the analog-digital converter 6 the analog measurement signal coming from another of the inductive sensors, for example from the sensor 2b. The microcontroller thus successively analyzes each of the corresponding digital signals coming from the analog-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 value and the maximum value of said digital signal.

[0048] The microcontroller 7 thus controls the multiplexer to select the inductive current sensor corresponding to the maximum deviation A, so that the most precise 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 presents, in an illustrative and schematic manner, the calculations of the deviations A of the digital signals corresponding to measurements carried out by the inductive sensors 2a, 2b and 2c of the device illustrated in [Fig.l].

[0051] [Tables 1] Sensor 2a 2b 2c Current measurement range (A) O to 10 O 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 coding) 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, that is to say varying temporally between - IV and IV.

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

[0054] The voltage of the analog measurement signal emitted by each inductive sensor is between -1 and 1 V. For the first sensor 2a, capable of measuring an intensity between 0 and 10 A, the voltage of the analog measurement signal is saturated and is 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 codes 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 coded, i.e. in the example 212 (4096) bits.

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

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

[0058] [Fig. 2] illustrates another example of a device according to the invention. It differs from that illustrated in [Fig. 1] in that the measuring module 15 comprises a multi-caliber inductive sensor 20 in place of the separate inductive sensors 2a, 2b and 2c. The multi-caliber inductive sensor measures the intensity of the electric current by successively selecting the different measurement calibers and transmits each analog measurement signal according to a corresponding caliber 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] The device 1 comprises several measuring modules 151 and 152. In the illustrated example, two measuring modules are shown, but this number of measuring modules measurement 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 the conductors 3a and 3b of an electric cable 4. Each measuring module 151, 152 acquires the analog measuring signals of the intensity flowing in the corresponding conductor 3a, 3b respectively. Once digitized by the analog-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 measuring signal. The optimal analog signal from the measuring module 151 and the optimal analog signal from the measuring module 152 can then be transmitted remotely by the microcontroller to the remote device 8.

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

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

Claims

Claims

1. 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-caliber inductive sensor (20) having different current intensity measurement calibers, to be arranged around a conductor (4), a multiplexer (5) comprising 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 flows in the conductor and / or an input channel for receiving the analog measurement signals acquired according to the different measurement calibers of the multi-caliber inductive sensor when a current flows in the conductor,the multiplexer being configured to output only one of said analog measurement signals, an analog-to-digital converter (6) for converting the analog measurement signal provided 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 which has the maximum measurement accuracy, and - controlling the multiplexer to select the optimal analog measurement signal.,

2. Device according to claim 1, further comprising a radio frequency communication module (8) for transmitting 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 micro- controller (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 having the largest deviation A.

4. Device according to the preceding claim, the microcontroller (7) being configured to calculate the deviation A without saturation of the analog or digital signals over different measurement time intervals and, for each of the measurement time intervals, 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 winding.

6. Device according to any one of the preceding claims, comprising several measuring modules (151, 152) for measuring the intensity of the current 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 select, for each measuring module, the corresponding optimal measurement signal.

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

8. A method of 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 which the inductive sensor(s) are arranged, an electric current flowing in the conductor, - receiving by the multiplexer (5) the analog measurement signals emitted by the corresponding inductive sensor(s), - controlling the multiplexer (5) by the microcontroller (7) to transmit to the analog-digital converter (6), successively, each of the analog measurement signals received at the input of the mul- triplexer, - 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 difference A between the maximum and minimum values ​​of the corresponding digital signal, the optimal analog measurement signal corresponding to the unsaturated digital signal having the greatest difference A.

10. Method according to the preceding claim, the microcontroller (7) being configured to calculate the deviation A without saturation of the analog or digital signals over different measurement time intervals and, for each of the measurement time intervals, control the multiplexer (5) so as to select the corresponding optimal analog measurement signal.

11. Method according to any one of claims 8 to 10, the conductor (4) being a conductor of a single-phase or polyphase electric 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 the inductive sensors (2a, 2b, 2c) of one of the devices are arranged, and - a monitoring module (9) configured to receive the output signals transmitted by each of the devices.

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

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

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