RU2819085C2 - Arc fault detection devices and associated arc fault protection units - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to arc fault detection devices, in particular, in electrical installation. Invention also relates to arc fault protection units containing such a detection device. Device comprises a high-frequency measuring system connected to at least two electrical phase lines of the installation and configured to extract a first signal representative of high-frequency components of electric currents flowing along said phase lines; plurality of low-frequency measuring systems, each connected to one electric phase line of the installation, wherein each is configured to receive a second signal representing an alternating line current flowing along a corresponding phase line; data processing module is programmed to detect arc fault based on the second signals and the first signal.

EFFECT: simplified fabrication of device for detection of arc fault in multiphase electrical installation.

12 cl, 6 dwg

Description

Aspects of the invention relate to devices for detecting an arc fault, in particular in an electrical installation. The invention also relates to arc fault protection units containing such a detection device.

In general, the invention applies to the field of arc fault protection and is aimed in particular at providing the ability to detect arc faults in a multi-phase AC electrical installation.

Arc fault protection units, such as circuit breakers, are sometimes configured to detect arc faults that may occur in a multiphase electrical installation. This detection is based on a measuring device containing low frequency current sensors and high frequency current sensors that are associated with the various phase conductors of the electrical installation. An arc fault on a phase line produces specific changes in LF and HF current that are most detectable on a closed phase line.

However, existing detection devices are not always satisfactory, especially in terms of the number of sensors and the complexity of the associated processing circuits.

Therefore, there is a need for a device for detecting arc faults in an AC system that exhibits satisfactory levels of performance while being easy to manufacture.

To this end, one aspect of the invention relates to a device for detecting an arc fault in a multi-phase electrical installation, said device comprising:

- a high-frequency measuring system connected to at least two of the electrical phase lines of the installation, said measuring system being configured to extract a first signal representing the high-frequency components of the electrical currents flowing through said phase lines, in particular when an arc fault is present;

- a plurality of low-frequency measuring systems, each connected to one electrical phase line of the installation, each configured to receive a second signal representing an alternating line current flowing along the corresponding phase line;

- a data processing module programmed to detect an arc fault based on the second signals and the first signal.

Thus, a single high-frequency measuring system is used for all electrical phase lines. Therefore, it is not necessary to use one high-frequency measurement system for each phase line, since this will multiply the number of current sensors and signal processing systems, which will increase the complexity and cost of manufacturing the detection device. The solution, however, provides the ability to detect arc faults quite reliably and efficiently.

In useful, but not required, aspects, such a detection device may combine one or more of the following features, taken alone or in some technically feasible combination:

- The measuring device contains a plurality of single-phase current sensors, each configured to be associated with one electrical phase line of the electrical installation, and in which the high-frequency measuring system is configured to combine the high-frequency measurement signals received from the current sensors to form a composite signal from which the said first signal.

- The outputs of the current sensors are connected to the input of the high-frequency measuring system via capacitors.

- The outputs of the current sensors are connected to the input of the high-frequency measuring system via resistors.

- The outputs of the current sensors are connected to the high-frequency measuring system by means of a magnetic connecting device, and each of said outputs is connected to a primary winding, said primary windings are magnetically connected to a secondary winding connected to the input of the high-frequency measuring system.

- The high frequency measurement system comprises a dedicated current sensor, such as a measurement toroid, configured to connect to at least two of the electrical phase lines, and configured to generate a composite signal from which said first signal is extracted, and in which the detection device comprises a plurality of single-phase current sensors, each configured to be associated with one electrical phase line of the circuit, each single-phase current sensor associated with one of the low-frequency measurement systems.

- Single-phase current sensors are current transformers.

- Each current sensor includes a magnetic toroid and a sensing coil wound around the magnetic toroid and configured to provide a wideband measurement signal at its terminals, the sensing coil containing less than forty turns, or preferably less than twenty turns.

- The high-frequency measurement system contains a band-pass filter configured to remove from the received signal components having a frequency below a predetermined threshold value.

- The high frequency measurement system comprises a demodulator, such as a logarithmic amplifier or a heterodyne mixer, configured to demodulate said first representative signal before transmitting it to the processing module.

- High frequencies are frequencies greater than or equal to 1 MHz, or greater than or equal to 5 MHz, preferably frequencies between 5 MHz and 40 MHz.

According to another aspect, the arc fault protection unit includes an electrical switching device adapted to interrupt the flow of current through a polyphase electrical installation upon receiving a trip signal, and a detection device as described above and connected to the switching device.

The invention will be better understood and other advantages thereof will become more clearly apparent in light of the following description of one embodiment of a detection device, provided by way of example only and with reference to the accompanying drawings, in which:

Fig. 1 is a schematic diagram of an arc fault detection device for an electrical installation according to one embodiment;

Fig. 2 is an electrical diagram of one embodiment of the high frequency measurement stage of the detection device of FIG. 1;

Fig. 3 is a schematic representation of another embodiment of the arc fault detection apparatus of FIG. 1;

Fig. 4 is a schematic representation of another embodiment of the arc fault detection apparatus of FIG. 1;

Fig. 5 schematically illustrates a comparison between an arc fault detection device according to embodiments and another detection device;

Fig. 6 is an enlarged view of the graph of FIG. 5.

Fig. 1 shows a multi-phase electrical installation 2, such as an electrical distribution installation 2 or, more generally, an AC electrical system.

The installation 2 contains a plurality of electrical conductors 4, each associated with one electrical phase line or pole, in order to allow the flow of multi-phase current, in particular, the flow of three-phase current.

In the examples described below, installation 2 contains three phase lines, designated L1, L2 and L3 with an optional "neutral" conductor (Fig. 3).

This example is not limiting and, alternatively, a different number of phase lines may be provided. The embodiments described below can be transferred to a polyphase system other than a three-phase system, for example, a two-phase system or a four-pole system containing three phase lines and a neutral line.

For example, conductors 4 are connected to an electrical load 6, designated "LOAD", for supplying multiphase electrical current.

In numerous embodiments, an arc fault protection unit is associated with the installation 2 in order to protect it from arc faults. For example, such arc faults can occur between two phase lines, or between one phase line and a protected electrical load, or between one phase line and ground.

For example, the protection unit may include an electrical switching device 8 and a detection device 10 connected to the switching device 8.

The switching device 8, designated "TRIP", is configured to interrupt the flow of current through the installation 2, and more specifically, through the conductors 4, upon receiving a trip signal, designated as "TRIP_SIGNAL" here.

For example, the switching device 8 comprises separate electrical contacts connected to a mechanical or electromechanical tripping mechanism.

The detection device 10 is in particular configured to detect an arc fault in the installation 2.

In accordance with numerous embodiments, detection device 10 includes:

- current sensors 12;

- a so-called high-frequency (HF) measuring and/or processing system 14, this system 14 is connected to at least two of the electrical phase lines L1, L2, L3 of the installation, or even to all of the mentioned phase lines, the mentioned measuring system 14 is configured to extract, in particular by means of demodulation, a first signal representing the high-frequency components of the electric currents flowing along said phase lines, this measuring system 14 here comprising a device 16 for combining high-frequency measurement signals obtained from various sensors in order to form a high-frequency composite signal from which subsequently, said representative signal will be extracted, and a pre-processing stage 18;

- a plurality of low-frequency measuring systems 20, each connected to an electrical phase line of the installation, each configured to receive a second signal representing an alternating line current flowing along the corresponding phase line;

- a data processing module 22 configured to detect an arc fault based on the second signals and the first high-frequency signal.

In practice, when an arc fault occurs in installation 2, high-frequency current components, and more specifically high-frequency noise, are superimposed on the line current flowing through phase lines L1, L2 and L3 of installation 2.

In numerous examples, as illustrated in FIGS. 1, the current sensors referred to collectively herein at reference 12 and individually designated CT1, CT2 and CT3 are single-phase current sensors. For example, each of these sensors is associated with one electrical phase line L1, L2, L3, for example, by connecting each near the corresponding conductor 4.

For example, system 10 includes one current sensor 12 for each of the phase lines L1, L2 and L3. In other words, the system 10 contains three sensors 12.

Preferably, each of the sensors 12 is configured to measure the alternating current flowing in the phase line with which it is associated with a wide frequency measurement range, in particular for measuring high frequency components of the alternating current, such as high frequency noise generated when an arc fault is present on the phase line.

For example, as used herein, "high frequencies" are frequencies greater than or equal to 1 MHz, or greater than or equal to 5 MHz, preferably frequencies between 5 MHz and 40 MHz, or even frequencies between 10 MHz and 20 MHz.

Low frequencies are, for example, frequencies below or equal to 50 kHz, or below or equal to 10 kHz, or even below or equal to 1 kHz.

For example, the sensors 12 have a wide frequency measurement range and can thus measure both high-frequency components and other components, in particular low-frequency components of line currents flowing through conductors 4.

Preferably, the frequency measurement range of the sensors 12 is between 50 Hz and 50 MHz.

In this example, device 10 contains three low frequency measurement systems, individually designated 24, 26 and 28, each associated with one electrical phase line L1, L2, L3, current sensors CT1, CT2 and CT3 connected to systems 24, 26 and 28 , respectively.

This example is non-limiting and, alternatively, the number of current sensors 12 could be changed differently; for example, only two current sensors 12 can be used. The same is assumed for the number of low-frequency measuring systems 20.

In practice, device 10 may contain as many low frequency measurement systems 20 as there are current sensors 12. In particular, it will be understood that each low frequency measurement system 20 is associated with one phase line L1, L2 or L3 of the installation.

It is also understood that the system 10 here comprises a single high-frequency measuring system 14, which is common to all phase lines L1, L2 and L3 of the installation, or at least to all phase lines for which the high-frequency component of the current is measured.

In numerous embodiments, the current sensors 12 are current transformers, or Rogowski coils. For example, the output of each current sensor 12 provides a wide-range measurement signal, such as a voltage representing a low-frequency electrical current flowing through the conductor 4 to which the current sensor 12 is connected, superimposed on this voltage by a high-frequency signal that is also present in the same conductor.

For example, each current sensor 12 includes a magnetic toroid and a sensing coil wound around the magnetic toroid, preferably made of ferrite material, and configured to provide a measurement signal at its terminals.

Preferably, the sensing coil of each current sensor 12 contains less than forty turns, or preferably less than twenty turns, which allows stray capacitances to be limited and the ability to prevent accidental removal of high-frequency components of the measured signal, thereby allowing the quality of the measured signal to be improved.

In embodiments as illustrated in FIGS. 1, the sensors 12 are common to the high frequency measurement system 14 and the low frequency measurement systems 20. In other words, the outputs of the sensors 12 are connected to both the input of the high frequency system 14 and the corresponding inputs of the low frequency systems 24, 26 and 28.

Therefore, it is understood that the system 14 is configured to extract the high frequency component of the signals measured by the sensors 12 and, more specifically, to perform this extraction from the composite signal output by the device 16.

In practice, each low frequency measurement system 24, 26, 28 herein is configured to collect a signal measured by one of the current sensors 12 and format that signal before providing it to the processing module 22.

In other words, in this example, current measurements are made by current sensors 12, and each of systems 24, 26 and 28 processes the signals measured by current sensor 12 specific to the phase line L1, L2 or L3 with which it is associated.

For example, each low frequency measurement system 24, 26, 28 may include active integrators that are adapted to amplify and/or filter and/or retrend line currents flowing through respective conductors 4 based on the low frequency measurement signals output from the sensors. 12 currents, or at least to retrend the low frequency components of these line currents.

In numerous embodiments, the data processing module 22 is implemented by one or more electronic circuits.

For example, module 22 includes a processor, such as a programmable microcontroller or microprocessor.

The processor is coupled to computer memory, or any computer-readable storage medium, that contains executable instructions and/or software code designed to implement a method for detecting an arc fault when those instructions are executed by the processor.

Alternatively, module 22 may include a signal processor (DSP), or a field programmable logic component (FPGA), or an application specific integrated circuit (ASIC), or any equivalent component configured and/or programmed to implement said detection method.

Module 22 includes a first interface 30 for receiving a first representative signal output from the high frequency measurement system 14. Module 22 also includes one or more second interfaces 32, 34, and 36, respectively configured to receive second signals output from the low frequency measurement systems 20.

For example, interfaces 30, 32, 34 and 36 each include an analog-to-digital converter configured to receive and sample a corresponding signal.

Embodiments of device 16 are now described with reference to FIG. 1, 2 and 3.

The device 16 allows the high frequency measurement system 14 to combine the high frequency measurement signals received from the various sensors 12 in order to generate said composite signal, which is common to the various phase lines, based on the electrical currents measured for each of the phase lines with which 12 sensors are associated.

More specifically, device 16 provides the ability to combine high-frequency measurement signals received from various sensors 12 to form said composite signal.

Preferably, this summation is performed in a similar manner, i.e., using discrete electrical or electronic components such as impedance dipoles, without resorting to electronic digital processing circuitry, thereby providing an implementation option that is less expensive and does not waste the computing resources of module 22 .

It will be understood that, in general, the device 16 is connected downstream of the sensors 12 and upstream of the pre-processing stage 18. For example, sensors 12 and device 16 form a measurement stage for the measurement system 14, this measurement stage is connected to said phase lines L1, L2, L3.

According to the first example, which is illustrated in FIG. 2, the outputs of the current sensors 12 are connected to a common point 42 through resistors placed in the form of a star, the common point 42 is connected to the input of the measuring system 14.

Thus, device 16, designated by reference 40 in this particular embodiment, includes resistors _ZC1 , _ZC2 , _ZC3 , each resistor connected between common point 42 and sensor CT1, CT2 and CT3, respectively.

In this example, the impedance Z _IN refers to the input impedance of the preprocessing stage 18 measured between common point 42 and the system's electrical ground GND. Impedances Z _M1 , Z _M2 and Z _M3 refer to the output impedances of sensors CT1, CT2 and CT3, respectively.

According to a second example, not illustrated, device 16 is a magnetic coupling device.

For example, the outputs of the current sensors 12 are connected to the high frequency measurement system 14 via a magnetic coupling device comprising primary windings and a secondary winding. Each of the outputs of the sensor 12 is connected to the primary winding. The primary windings are magnetically connected to the secondary winding, which itself is connected to the input of the measuring system 14.

To improve the connection, the device 16 may include a magnetic core around which the corresponding primary windings of the current sensors 12 and a secondary winding are wound.

According to the third example illustrated in FIG. 3, the outputs of the current sensors 12 are connected to a common point 52 through capacitors 54 placed in the form of a star, the common point 52 is connected to the input of the measuring system 14.

Thus, device 16, designated by reference 50 in this particular embodiment, includes, preferably identical, capacitors 54, each capacitor 54 connecting between a common point 52 and sensor CT1, CT2 and CT3, respectively.

It is preferable to use capacitors 54 to combine the signals measured by the current sensors 12 because the impedance of capacitors is inversely proportional to frequency, so that the impedance at high frequency is relatively low, which favors high frequency coupling while still providing good isolation between different signals line current for low frequencies.

_The reference U _{IN_HF} refers to the composite signal obtained at the output of the device 16 based on the electrical currents measured by the current sensors 12.

In embodiments, the composite signal U _{IN_HF} corresponds to a combination of high-frequency contributions for the various phase lines L1, L2 and L3 of the installation. In other embodiments, the composite signal U _{IN_HF} corresponds to a combination of individual currents measured for different phase lines L1, L2 and L3 of the installation, without frequency discrimination, the extraction of high frequency contributions being obtained only through post-processing (such as filtering) in the pre-processing stage 18.

For example, the composite signal U _{IN_HF} is a voltage.

Note that, in the example of FIG. 3, the electrical installation 2' differs from the installation 2 in that the electrical conductors 4' furthermore contain, in addition to the three phase lines L1, L2 and L3, a neutral line, designated N here. This neutral line N can be omitted without changing the operation of the detection system 10' or changing the operation of the device 16, however.

In embodiments that are neither illustrated nor described in detail, device 16 may also be implemented in other ways, for example, with more complex circuitry, such as one or more bandpass filters in the frequency domain used to detect arc faults.

Embodiments of preprocessing step 18 are now described with reference to FIGS. 3.

In numerous embodiments, not just the embodiment of FIG. 3, the pre-processing stage 18 is configured to extract, in particular by demodulation, a first signal representing high-frequency components of the electric currents flowing through said phase lines from the composite signal U _{IN_HF} before being received by the processing module 22.

For example, the pre-processing stage 18 includes at least one filter 56 configured to remove from the received composite signal U _{IN_HF} components having a frequency below a predetermined threshold value, such as a predetermined threshold value of 5 MHz or 1 MHz.

In the illustrated examples, filter 56 is a bandpass filter. This bandpass filter can be configured to only allow frequencies of the U _{IN_HF} composite signal to pass between 1 MHz and 50 MHz, or preferably between 5 MHz and 40 MHz, or even frequencies between 10 MHz and 20 MHz.

Thus, the filter 56 provides the ability to extract high-frequency components from the composite signal originating from the measurements obtained by the current sensors 12.

The pre-processing stage 18 also includes a demodulator 58, such as a logarithmic amplifier or heterodyne mixer, configured to demodulate the signal before transmitting it to the processing module 22. For example, a pre-processing stage 18 is connected downstream of filter 56.

In particular, demodulator 58 provides the ability to extract the envelope of the first signal U _{IN_HF} . The corresponding envelope signal, denoted RSSI here in FIG. 3 is then sent to input 30 of processing module 22.

The preprocessing stage 18 therefore makes it possible to extract, in particular by demodulation, from the first signal originating from the combination of signals measured individually by the current sensors 12, information about the power value or the root mean square value of the amplitude (envelope) of said first signal.

With respect to the composite signal U _{IN_HF} , the demodulated signal waveform (RSSI) is smoother, i.e., at frequencies well below 1 MHz, for example at least 100 times below 1 MHz. The demodulated waveform is simpler to sample and requires less computational resources compared to sampling a composite signal U _{IN_HF} . However, the waveform itself contains enough useful information to enable arc fault detection with reasonable reliability. The processing unit 22 therefore does not have to receive the entire first signal.

Thanks to the invention, a single high-frequency measuring system 14 is used for all electrical phase lines L1, L2 and L3. Therefore, it is not necessary to use one high-frequency measurement system for each phase line, since this will correspondingly multiply the number of signal processing and pre-processing components in the detection device. Currently, the components required to process high-frequency signals are typically expensive. Such multiplication will therefore increase the complexity and cost of manufacturing the detection device.

Various embodiments of the detection device 10 or 10', however, provide the ability to detect arc faults quite reliably and efficiently, even using only one high-frequency signal processing circuit common to multiple phase lines, and based on the first signal U _{IN_HF} without directly using signals measured individually for each phase line.

Indeed, the occurrence of an arc fault in one of the phase lines L1, L2 or L3 generates noise on the currents flowing through different phase lines. This noise is randomly shifted in phase between different phase lines at high frequencies, and can also be amplified or attenuated randomly from one phase line to another, so that the sum of the high frequency components of these currents is not zero. In contrast, no such phase shift is present in the low frequency components of these identical currents, the latter remaining consistent with each other from one phase line to the next. The sum of the low-frequency components of these identical currents is thus equal to zero.

Measuring high-frequency noise from electric currents flowing through phase lines L1, L2, L3 thus provides the ability to easily identify arc faults without the need to use, for high frequencies, measurement and signal processing tools that are overly complex and dedicated to each of the phases. lines.

According to the exemplary embodiments, an arc fault can be detected by the detection algorithm implemented in the processing unit 22 by comparing the measured signals output by the low frequency measurement circuit with the first signal associated with the high frequency components.

In particular, module 22 may be configured to detect whether the sum of the low-frequency currents is zero while, at the same time, the sum of the high-frequency components of those same currents (which is provided by the first signal, or by its envelope, or by whatever - or the corresponding representative quantity generated by the pre-processing step 18) is not zero.

The waveform of the high frequency composite signal can advantageously be used as an arc fault indicator. The presence of an arc fault is detected by a processing algorithm implemented in module 22. As a response to the detection algorithm, module 22 may be configured to send a trip signal TRIP_SIGNAL to the switching device 8 in order to interrupt the flow of current through the conductors 4.

Otherwise, such a signal is not transmitted, and the system continues to operate.

However, other detection methods may be used.

Fig. 4 shows a detection device 10'' according to another embodiment, which differs from the embodiments described previously in that the high frequency measurement system 14 includes a dedicated current sensor 60, such as a measurement toroid.

The current sensor 60 is configured to connect to at least two of the electrical phase lines L1, L2, L3, or even all of the electrical phase lines, and replaces the sensors 12 and the device 16. In other words, in this embodiment, the device 16 is lowered as and 12 current sensors.

In other words, sensor 60 is used both to measure the electrical currents flowing through said phase lines and to combine components specific to each phase line to form a composite signal U _{IN_HF} .

Therefore, it is understood that, in this embodiment, a single current sensor 60 forms the measurement stage for the high frequency measurement system 14. A preprocessing stage 18 is connected at the output of the current sensor 60.

For example, sensor 60 is a differential measurement toroid, such as those used in differential circuit breakers. In the illustrated example, sensor 60 includes a magnetic toroid surrounding said phase lines and a sense coil 62 connected to the input of the pre-processing device.

In the illustrated example, detection device 10'' also includes a plurality of single-phase current sensors LFS1, LFS2, LFS3, collectively designated 64, which are similar to sensors 12 described previously.

However, in this embodiment, the current sensors 64 are not connected to the high frequency measurement system 14, since the latter has its own current sensor 60.

In practice, each of the current sensors 64 is configured to associate with one electrical phase line of the circuit while at the same time connecting to one of the low frequency measurement systems 20.

In this example, the device 10'' contains three low frequency measurement systems 24, 26 and 28, as previously described, each of them associated with one electrical phase line L1, L2, L3, current sensors LFS1, LFS2 and LFS3 are connected to the measurement systems 24, 26 and 28, respectively. On the other hand, current sensors LFS1, LFS2 and LFS3 are not connected to the high-frequency measuring system 14.

Apart from these differences, the operation of the detection device 10'' is similar, or even identical, to the operation of the detection devices 10 and 10' described previously, particularly as regards the role and operation of the processing module 22 and the pre-processing device 18.

In particular, it is understood that, in this embodiment, the detection device 10'' in this case also comprises a single measuring system 14 common to all phase lines L1, L2 and L3 of the installation, or at least for all phase lines for which the high frequency component of the current is measured.

Fig. 5 illustrates an example of comparison of the results obtained in order to detect an arc fault between, on the one hand, a detection device 72 in accordance with the embodiments that are described previously, and, on the other hand, another detection device 74 in which each of the phase lines 76 Installation 70 is associated with a sensor and a dedicated HF measurement system, which are respectively designated "HF Circuit1", "HF Circuit2" and "HF Circuit 3". In contrast, detection device 72 contains a single high frequency measurement system, designated "HF Circuit", for all phase lines of the installation.

In the illustrated example, it is considered, for illustrative purposes, that the arc fault 78, designated "Arc Fault", has occurred on the second phase line L2 between said phase line and ground. This example is non-limiting and, in practice, an arc fault can be detected on any phase line.

Plot 80 illustrates the trend, as a function of time (x-axis, in milliseconds, denoted "time"), in the amplitude of the signals output by two devices 72 and 74. FIG. 6 is an enlarged view of area 82 of graphics 80.

In the illustrated example, the signal designated "RSSI _MAX " corresponds to the signal provided by device 72, and corresponds here to the first RSSI signal representing high frequency components of electrical currents flowing through said phase lines, as defined in the previous embodiments.

The other signals "RSSI ₁ ", "RSSI ₂ " and "RSSI ₃ " correspond, respectively, to signals provided by each of the high frequency measurement systems of the other device 74.

In the graph, the RSSI ₂ signal associated with the second phase line L2 has a maximum amplitude after the fault occurs (slightly after a time of 1 second), while the amplitude of the RSSI ₁ and RSSI ₃ signals, which are associated with the adjacent phase lines L1 and L3, is lower.

The amplitude of the first signal RSSI _MAX output by the single measuring system 14 of device 72 is, for its part, close to the amplitude of the RSSI ₂ signal.

Thus, the first signal output by the measurement system 14 can be used instead of the RSSI ₁ , RSSI ₂ and RSSI ₃ signals demodulated for each phase line, however, without interfering with arc fault detection.

Any feature of one of the embodiments or variants described above may be implemented in other embodiments and variants described.

Claims (15)

1. A device (10; 10'; 10'') for detecting an arc fault in a multiphase electrical installation (2), this device containing: - a high-frequency measuring system (14) connected to at least two electrical phase lines (L1, L2, L3) of the installation, wherein said measuring system is configured to extract a first signal (RSSI) representing high-frequency components of electric currents flowing through said phase lines lines; a plurality of low-frequency measuring systems (20), each connected to one electrical phase line of the installation, each configured to receive a second signal representing an alternating line current flowing along the corresponding phase line; a data processing module (22) programmed to detect an arc fault based on the second signals and the first signal. 2. The device according to claim 1, in which the measuring device contains a plurality of single-phase current sensors (12; CT1, CT2, CT3), each configured to be associated with one electrical phase line (L1, L2, L3) of the electrical installation, and in which The high frequency measurement system is configured to combine high frequency measurement signals received from the current sensors to form a composite signal (U _{IN_HF} ) from which said first signal (RSSI) is extracted. 3. The device according to claim 2, in which the outputs of the current sensors (12; CT1, CT2, CT3) are connected to the input of the high-frequency measuring system via capacitors (54). 4. The device according to claim 2, in which the outputs of the current sensors (12; CT1, CT2, CT3) are connected to the input of the high-frequency measuring system via resistors (Z _C1 , Z _C2 and Z _C3 ). 5. The device according to claim 2, in which the outputs of the current sensors (12; CT1, CT2, CT3) are connected to the high-frequency measuring system via a magnetic connecting device, and each of said outputs is connected to the primary winding, said primary windings are magnetically connected to the secondary winding connected to the input of the high-frequency measuring system. 6. The device according to claim 1, in which the high-frequency measuring system (14) includes a dedicated current sensor (60), such as a measuring toroid, configured to connect to at least two of the electrical phase lines and configured to generate a composite signal ( U _{IN_HF} ) from which said first signal (RSSI) is extracted, and in which the detection device (10'') comprises a plurality of single-phase current sensors (64; LFS1, LFS2, LFS3), each configured to be associated with one electrical phase line circuit, each single-phase current sensor is associated with one of the low-frequency measuring systems (20). 7. Device according to any one of paragraphs. 2-6, in which single-phase current sensors (12; CT1, CT2, CT3; 64; LFS1, LFS2, LFS3) are current transformers. 8. The device according to claim 7, in which each current sensor (12; CT1, CT2, CT3; 64; LFS1, LFS2, LFS3) contains a magnetic toroid and a measuring coil wound around the magnetic toroid and configured to provide a wideband measurement signal to their terminals, the measuring coil containing less than forty turns, or preferably less than twenty turns. 9. An apparatus as claimed in any one of the preceding claims, wherein the high-frequency measurement system (14) includes a band-pass filter (56) configured to remove components from the received signal having a frequency below a predetermined threshold value. 10. The apparatus of claim 1, wherein the high frequency measurement system (14) comprises a demodulator (58), such as a log amplifier or heterodyne mixer, configured to demodulate said first representative signal before transmitting it to the processing module. 11. The device according to any of the preceding claims, wherein the high frequencies are frequencies greater than or equal to 1 MHz, or greater than or equal to 5 MHz, preferably frequencies between 5 MHz and 40 MHz. 12. Arc fault protection unit (8+10), containing an electrical switching device (8), configured to interrupt the flow of current through a multiphase electrical installation (2) when receiving a shutdown signal, and a device (10; 10'; 10'') detection in accordance with any of the preceding paragraphs and connected to the switching device.