AU2015234297A1 - Device and method for monitoring the state of an electrical protection or power supply circuit in an electrical energy distribution network or circuit, and corresponding distribution network and circuit - Google Patents

Abstract

The invention relates to a device and a method for monitoring the state of an electrical circuit supplied with electrical energy by an electrical energy source, such as a circuit for protection against electrical overloads at the output of an electrical energy source in an electrical energy distribution network, or an electrical power supply circuit of an electronic apparatus at the output of the electrical energy source in an electrical energy distribution circuit. This monitoring device comprises means for measuring an electrical quantity, such as the electrical energy, associated with the electrical circuit supplied by the electrical energy source, the measurement means comprising a power supply circuit 14 able to generate an electrical power supply current and a measurement circuit, for example of Rogowski type, able to measure the electrical quantity associated with the power supply circuit 14. This power supply circuit 14 comprises detection means 20 able to detect the absence or the presence of current in the electrical circuit by measuring the voltage across the terminals of the power supply circuit 14. + 0 0 ~~ -o /~; - ------------ -- ---- - - --------

Description

1 Device and method for monitoring the state of an electrical protection or power supply circuit in an electrical energy distribution network or circuit, and corresponding distribution network and circuit [0001] The present invention relates to a device and a method for monitoring the state of an electrical circuit supplied with electrical energy by an electrical energy source, such as a circuit for protection against electrical overloads at the output of an electrical energy source in an electrical energy distribution network, or such as an electrical power supply circuit of an electronic apparatus at the output of the electrical energy source in an electrical energy distribution circuit. The invention relates also to such an electrical energy distribution network and circuit. [0002] It is notably applicable to the monitoring of the protection devices arranged at the output of a medium voltage (MV)/low voltage (LV) transformer intended for the distribution of electrical energy to all or part of the network. [0003] It is also applicable to the monitoring of standby-switching devices with which electronic apparatuses, such as domestic electronic apparatuses, are equipped. [0004] An electrical energy distribution, or electrical distribution, network in residential districts generally comprises an MV/LV transformer which delivers a number of low voltage outputs (230 V between a phase and neutral and 380 V between two phases). These outputs are generally protected simply by fuses at the transformer. Protection circuit breakers are installed downstream on each branch of the electrical network, to protect these branches. [0005] The fuses arranged at the output of the transformer are subject to little stress, but can nevertheless blow under the effect of a significant overload not eliminated by one of the circuit breakers installed downstream.

2 [0006] Also, it is useful for the energy distributor to be informed of the blowing of the fuse as soon as possible. To this end, each output (or outgoing feeder) of the transformer can be equipped with a blown fuse detection system, as described for example in WO 2005/027295. [0007] However, the event is rare, and there is therefore no economic benefit in equipping each outgoing feeder with such a blown fuse detection system. [0008] There are simple, and therefore less expensive, solutions for monitoring fuses by voltage measurement, such as that described in DE 4104184. Nevertheless, such solutions work only in the case of a single-phase distribution and cannot be used in the more general case of three phase distribution. [0009] It is moreover known that the energy distributors generally equip the different outgoing feeders with systems for measuring the energy in order to optimize the management of the electrical network. Such systems notably make it is possible to produce diagnoses, optimize the load, implement a load-shedding, detect energy theft, etc. [0010] Some of these systems also make it possible to report on the state of the network, to make it possible to determine, for example, if a protection has cut off a part of the electrical network, and, in this case, to make it possible to locate the fault. [0011] However, these systems do not always make it possible to measure the voltage, because such a measurement results in installation constraints and a significant cost overhead. In effect, it is in this case necessary for these systems to guarantee the insulation distances and withstand the network overvoltages in the event of lightning for example. Also, the measurement of the current is 3 normally used in association with algorithms that make it possible to deduce therefrom the state of the network. [0012] Such an algorithm, which can be more or less sophisticated to take account or not of the level of the overload, can be of the type: overload for a time t longer than a time tmax, then current = 0 A, means a high probability of having a protection which has opened the electrical circuit. [0013] In many protection and current measurement devices, the electronics are powered with one or more current sensors, therefore power supply sensors of iron type. This type of power supply is called self-current power supply. [0014] The measurement is, for its part, performed by another sensor, preferentially, a sensor of Rogowski type, therefore a measurement sensor for each phase of air type. [0015] An example of such a device is described in FR 2 982 665. [0016] The main issue with this type of device is the difficulty in obtaining any certainty that no current is passing through the measured phase. [0017] In effect, the measurement sensor used, of Rogowski type, presents the drawback of delivering a voltage if a conductor with a current flowing through it is nearby. This can, depending on the rating of the device, represent a current of the order of 0.1 to several amperes. This phenomenon is called crosstalk. [0018] Now, in the case of electrical distribution of three-phase type, the devices with which the circuits protected by fuses are equipped measure three phases. One phase may then be absent in a conductor, following an overload or a short circuit, but the measurement sensor will still detect a current because of 4 the powering of the other phases by the sensors. In other words, no distinction will be drawn between a missing phase and a low load. [0019] To avoid this, it would be possible to eliminate the crosstalk phenomenon by using sensors composed of a magnetic circuit. However, such sensors are more expensive and bulky, and exhibit a reduced dynamic range. [0020] Thus, in the conventional devices using a sensor of Rogowski type, it is not possible to know with certainty if the current of the conductor measured is indeed zero. [0021] Conversely, for the same reasons as those described above in the context of an application to the monitoring of the protection devices arranged at the output of an MV/LV transformer intended to distribute electrical energy to all or part of the network, the conventional standby-switching devices with which the domestic electronic apparatuses are equipped may sometimes not correctly detect the presence of current which should cause the apparatus concerned to be re-powered. [0022] One of the aims of the invention is therefore to resolve the abovementioned problems. Thus, the aim of the invention is notably to propose an electrical energy distribution device and method which make it possible to detect the absence of current in the protection devices by the isolation of the different power supply outgoing feeders, in particular in the case of a three-phase distribution, without equipping these different outgoing feeders with specific costly detection devices, or which make it possible to reliably detect the presence of current in the power supply devices of electronic apparatuses to reactivate these apparatuses after having been switched to standby. [0023] Thus, the subject of the invention, according to a first aspect, is a monitoring device intended to check the state of an electrical circuit supplied with electrical energy by an electrical energy source, such as an electrical circuit for 5 protection against electrical overloads of the type comprising at least one fuse and with which an output of the electrical energy source in an electrical distribution network is equipped, or such as an electrical power supply circuit of an electronic apparatus at the output of the electrical energy source, said monitoring device comprising means for measuring at least one electrical quantity, such as the electrical energy, associated with the electrical circuit supplied by the electrical energy source, said measurement means comprising at least one power supply circuit suitable for generating an electrical power supply current and at least one measurement circuit, for example of Rogowski type, suitable for measuring said electrical quantity associated with said power supply circuit. [0024] The power supply circuit comprises detection means suitable for detecting the absence or the presence of current in the electrical circuit by measuring the voltage at the terminals of the power supply circuit. [0025] According to certain embodiments, the device further comprises one or more of the following features, taken in isolation or in all technically possible combinations: - the power supply circuit comprises power supply means and rectifying means, such as a Graetz bridge, suitable for rectifying the current delivered by the power supply means, and the detection means are arranged between the power supply means and the rectifying means; - the detection means comprise two resistor bridges in parallel between the power supply means and the rectifying means, and a differential amplification means, and the two resistor bridges are linked to the differential amplification means so as to make it possible to amplify the difference between the voltage in one of the two resistor bridges and the voltage in the other of these two resistor bridges; - each of the two resistor bridges comprises two resistors, and is linked to one of the two inputs of the differential amplification means by a link point situated between said two resistors; 6 the detection means comprise a comparison means suitable for comparing an input voltage value relative to a reference voltage value and for delivering as output a voltage when the difference between this input voltage and the reference voltage is positive, and the output voltage of the differential amplification means is linked to the input of the comparison means, such that the comparison means delivers as output a voltage when the difference between the output voltage of the differential amplification means and the reference voltage is positive; the detection means comprise at least one comparison means suitable for comparing an input voltage value relative to a reference voltage value and for delivering as output a voltage when the difference between this input voltage and the reference voltage is positive, and the voltage between one of the terminals of the power supply means and one of the terminals of the rectifying means is linked to the input of the comparison means, such that the comparison means delivers as output a voltage when the difference between the voltage between said terminal of the power supply means and said terminal of the rectifying means and the reference voltage is positive; the detection means comprise at least two comparison means each suitable for comparing an input voltage value relative to a reference voltage value and for delivering as output a voltage when the difference between this input voltage and the reference voltage is positive, the voltage between a first of the terminals of the power supply means and a first of the terminals of the rectifying means is linked to the input of a first of the comparison means, and the voltage between a second of the terminals of the power supply means and a second of the terminals of the rectifying means is linked to the input of a second of the comparison means, such that the first and second comparison means respectively deliver as output a voltage when the difference between the voltage between the first, respectively the second, of the terminals of the power supply means and the first, respectively to the second, of the terminals of the rectifying means and the reference voltage is positive; 7 - the detection means comprise a logic gate with two inputs respectively linked to the output voltages of the two comparison means, and suitable for delivering an output voltage when at least one of the two comparison means delivers an output voltage. [0026] Another subject of the invention, according to a second aspect, is an electrical energy distribution network comprising a number of branches and an electrical energy source suitable for delivering as output electrical energy for each branch, at least one of the outputs of the electrical energy source being equipped with an electrical circuit for protection against electrical overloads of the type comprising at least one fuse. [0027] The network comprises, for at least said output of the electrical energy source, a monitoring device as described above, so as to make it possible to detect the absence of current in the electrical circuit protecting said output of the electrical energy source. [0028] In a particular embodiment, the electrical energy source is suitable for delivering as output three-phase electrical energy for at least one of the branches of the distribution network. [0029] Another subject of the invention, according to a third aspect, is an electrical energy distribution circuit in an electronic apparatus, comprising an electrical power supply circuit and an electrical energy source suitable for delivering as output electrical energy to the electrical power supply circuit. [0030] The distribution circuit comprises a monitoring device as described above, so as to make it possible to detect the presence of current in the electrical power supply circuit. [0031] Another subject of the invention, according to a fourth aspect, is a method for monitoring the state of an electrical circuit supplied with electrical 8 energy by an electrical energy source, such as an electrical circuit for protection against electrical overloads of the type comprising at least one fuse and with which an output of the electrical energy source in an electrical energy distribution network is equipped, or such as an electrical power supply circuit of an electronic apparatus at the output of the electrical energy source, by means of a monitoring device comprising means for measuring at least one electrical quantity, such as the electrical energy, associated with the electrical circuit, said measurement means comprising at least one power supply circuit suitable for generating an electrical power supply current and at least one measurement circuit, for example of Rogowski type, suitable for measuring said electrical quantity associated with said power supply circuit. [0032] The method comprises a step of detection of the absence or of the presence of current in the electrical circuit by the measurement of the voltage at the terminals of the power supply circuit by detection means. [0033] According to certain implementations, the method further comprises one or more of the following features, taken in isolation or in all technically possible combinations: - the power supply circuit comprises two resistor bridges arranged between power supply means and rectifying means, such as a Graetz bridge, and the measurement of the voltage at the terminals of the power supply circuit comprises the amplification, by a differential amplification means, of the difference between the voltage in one of the two bridges and the voltage in the other of the two bridges; - the measurement of the voltage at the terminals of the power supply circuit comprises the comparison, by a comparison means, of the differential voltage amplified by the differential amplification means relative to a reference value, and the supply of an output voltage by the comparison means when the amplified differential voltage at the input is greater than the reference voltage; 9 the power supply circuit comprises power supply means and rectifying means, such as a Graetz bridge, and the measurement of the voltage at the terminals of the power supply circuit comprises the comparison, by a comparison means, of the voltage value between one of the terminals of the power supply means and one of the terminals of the rectifying means, and the supply of an output voltage by the comparison means when the difference between the voltage between said terminal of the power supply means and said terminal of the rectifying means and the reference voltage is positive; the power supply circuit comprises power supply means and rectifying means, such as a Graetz bridge, and the measurement of the voltage at the terminals of the power supply circuit comprises the comparison, by a first comparison means, of the voltage value between a first of the terminals of the power supply means and the first of the terminals of the rectifying means, the comparison, by a second comparison means, of the voltage value between a second of the terminals of the power supply means and a second of the terminals of the rectifying means, and the supply of a respective output voltage by the first and second comparison means when the difference between the voltage between the first, respectively the second, of the terminals of the power supply means and the first, respectively the second, of the terminals of the rectifying means and the reference voltage is positive; the measurement of the voltage at the terminals of the power supply circuit comprises the supply, by a logic gate with two inputs linked respectively to the output voltages of the two comparison means, of an output voltage when at least one of the two comparison means delivers an output voltage; the monitored electrical circuit is a power supply circuit of an electronic apparatus, and the method comprises the switching of the electronic apparatus to standby based on the absence of voltage at the output of the logic gate.

10 [0034] Thus, the use of the sensor or power supply circuit of the measurement device, situated on each power supply outgoing feeder to the branches of the network, therefore of an iron circuit which exhibits no sensitivity to crosstalk, makes it possible to detect the absence of current in the fuse protection of the outgoing feeder concerned by clearly establishing the difference between a missing phase and a very low load. [0035] Also, the use of this sensor or power supply circuit of the measurement device, situated in the power supply circuit of an electronic apparatus, makes it possible to detect the presence of current for the resupplying of the apparatus after having been switched to standby, or for not switching the apparatus to standby, or the absence of current for the switching to standby, by here again clearly establishing the difference between a missing phase and a very low load. [0036] The invention therefore makes it possible to ensure the diagnoses of the fuses of the protection devices of each outgoing feeder, by using the resources of the electrical power/energy measurement system installed on each branch of the electrical energy distribution network, or the reliable implementation of a function for switching an electronic apparatus to standby. [0037] The features and advantages of the invention will emerge on reading the following description, given purely as a nonlimiting example, with reference to the following attached figures: - Figure 1: a schematic representation of an example of electrical energy distribution network according to the invention; - Figure 2: a schematic representation of a part of a first example of monitoring device according to the invention intended to equip a network such as that of Figure 1 on each outgoing feeder to the branches of this network; 11 - Figure 3: a schematic representation of a part of a second example of monitoring device according to the invention intended to equip a network such as that of Figure 1 on each outgoing feeder to the branches of this network; - Figure 4: a schematic representation of a part of a third example of monitoring device according to the invention intended to equip an electronic circuit with standby switching function; - Figures 5 to 7: show different measurements performed on a device such as that represented partially in Figure 2, respectively in the case of low primary current, of relatively high primary current, and of absence of primary current, in the monitored protection circuit. [0038] Figure 1 schematically represents an exemplary electrical energy distribution network according to the invention, with an electrical energy power source 1 embodied by a transformer 1 such as an MV/LV transformer. [0039] In this example, the network is three-phase, and makes it possible to distribute the electrical energy to a number of branches A to F of the network, which can for example correspond to the different districts of a town. [0040] Each of the outputs of the transformer 1 corresponds to an outgoing feeder to one of the branches A to F, and is equipped on the one hand with a circuit for protection against electrical overloads and a device for monitoring the protection circuit according to the invention which comprises means for measuring the electrical energy distributed as output to the corresponding branch. [0041] Thus, the outputs to the branches A to F are equipped respectively with the protection circuits 2 to 7, and respectively also with the monitoring devices comprising the measurement means 8 to 13. [0042] Each protection circuit 2 to 7 comprises at least one fuse 2 to 7 and is comparable to this fuse in Figure 1.

12 [0043] The monitoring device comprising the measurement means 8 of the protection circuit 2, at the level of the outgoing feeder o the branch A of the network, makes it possible to check the state of this protection circuit 2, and in particular the absence of current in this protection circuit 2, which would for example be linked to the blowing of the fuse 2 as a result of an electrical overload. [0044] The principle is identical for the other monitoring devices respectively comprising the measurement means 9 to 13 associated respectively with the other protection circuits 3 to 7 on the respective outgoing feeders to the other branches B to F of the network. [0045] The measurement means 8 to 13 each comprise a measurement sensor circuit, or measurement circuit, preferably of Rogowski type, that makes it possible to measure the electrical energy distributed to the corresponding branch A to F, and a power supply sensor circuit, or power supply circuit, that makes it possible to generate an electrical power supply current based on the electrical energy measured by the measurement circuit. [0046] A power supply circuit outputs a secondary current when it is capable of supplying a voltage greater than the power supply voltage. However, the simple measurement of the secondary current supplied by a power supply circuit is not sufficient, because, in the case of a low network load, this power supply circuit does not output any current. Also, it is the voltage at the terminals of the circuit that is of interest, to be sure to be able to determine if the primary current is zero or not. [0047] These considerations in Figure 1 relate also to the application to the switching of electronic apparatuses to standby, for example in a domestic energy distribution electrical circuit which is supplied by an electrical energy power supply source 1.

13 [0048] Each branch A to F of the energy distribution circuit corresponds to a distribution branch to one or more electronic apparatuses, with electrical power supply circuits 2 to 7 and measurement means 8 to 13 on the outgoing feeder of each of the branches A to F. [0049] A measurement means 8 to 13 according to the invention therefore comprises a particular power supply circuit, such as the power supply circuit 14 which will be described more specifically with reference to Figures 2 to 4. [0050] Conventionally, this power supply circuit 14 comprises power supply means 19, represented in the example of Figure 3 by a transformer 12 and a magnetizing induction coil Li in parallel, and the resistor R23. [0051] It also comprises rectifying means 18, such as a diode bridge 18 or Graetz bridge 18 formed by the four diodes D22, D26, D28, D29. [0052] These rectifying means 18 make it possible to rectify the current output by the power supply means 19 of the power supply circuit 14. [0053] The output of these rectifying means, identified by the label "power" in Figure 3, and linked to a current source 22 in Figures 2 to 4, makes it possible to charge a capacitor C1 that is not represented in the figures. [0054] Between the power supply means 19 and the rectifying means 18, there are detection means, referenced 15, 16, 17 in Figure 3 and 20, 21 in Figures 2 and 4. [0055] In the examples of Figures 2 and 3, these detection means 15, 16, 17 or 20 make it possible to detect the absence of current in the corresponding protection circuit, that is to say one of the protection circuits 2 to 7 of Figure 1 situated on the outgoing feeder of the electrical energy source 1 to one of the 14 branches A to F of the network, and associated with one of the measurement devices 8 to 13. [0056] In the example of Figure 4, these detection means 21 make it possible to detect the presence or the absence of current in the corresponding electrical power supply circuit, that is to say one of the circuits 2 to 7 of Figure 1 situated on the outgoing feeder of the electrical energy source 1 to one of the branches A to F of the distribution circuit, and associated with one of the measurement devices 8 to 13. [0057] This detection is thus obtained by the measurement of the voltage at the terminals of the power supply circuit 14. [0058] In the example of Figure 2, the detection means 20 comprise at least one comparison means 24. [0059] The function of this comparison means 24 is to compare an input voltage value relative to a reference voltage value and to deliver as output a voltage when the difference between this input voltage and the reference voltage is positive. [0060] Specifically, the comparison means 24 measures the difference between, on the one hand, the voltage between one of the terminals of the power supply means 19 and one of the terminals of the rectifying means 18, and, on the other hand, a reference voltage, and delivers as output a voltage when this difference is positive, therefore when there is current in one of the phases monitored by the device. [0061] Conversely, when no voltage is obtained as output from the comparison means 24, because of a difference less than or equal to zero between, on the one hand, the voltage between one of the terminals of the power supply means 19 and one of the terminals of the rectifying means 18, and, on the 15 other hand, a reference voltage, the absence of current in the phase monitored by the device is deduced therefrom. [0062] The information obtained by the detection means 20 is then transmitted to computation means 23 for processing and use. [0063] In the example of Figure 3, the detection means 15, 16, 17 comprise two resistor bridges 15, and a differential amplification means 16, placed between the power supply means 19 and the rectifying means 18. [0064] The differential amplification means 16 notably comprises an amplifier X1. [0065] The two resistor bridges 15 are linked to the differential amplification means 16 so as to allow the amplification of the difference between the voltage in one and the other of the two bridges 15. [0066] Thus, if the first bridge comprises the two resistors R7, R8 and the second bridge comprises the two resistors R9, R14, the differential amplification means 16 makes it possible to amplify the difference between the voltage in the first bridge R7, R8 and the voltage in the second bridge R9, R14, on the one hand by a link between a link point dif- between the two resistors R7, R8 of the first of the two bridges 15 and one dif- of the two inputs dif-, dif+ of the differential amplification means 16, and, on the other hand, by a link between a link point dif+ between the two resistors R9, R14 of the second of the two bridges 15 and the other dif+ of the two inputs dif-, dif+ of the differential amplification means 16. [0067] The detection means 15, 16, 17 also comprise a comparison means 17 whose function is to compare an input voltage value relative to a reference voltage value and to deliver as output a voltage when the difference between this input voltage and the reference voltage is positive.

16 [0068] The comparison means 17 notably comprises a comparator X2. [0069] Thus, the output voltage Uxi of the differential amplification means 16 is injected as input for the comparison means 17, which makes it possible for this comparison means 17 to deliver as output a voltage Ux 2 when the difference between the output voltage Ux1 of the differential amplification means 16 and the reference voltage is positive. [0070] More specifically, the comparison by the comparison means 17 and relative to a reference value, between the difference Ux1, amplified by the differential amplification means 16, between the voltage in the first R7, R8 of the two resistor bridges 15 and the voltage in the second R9, R14 of the two resistor bridges 15, makes it possible to obtain a voltage Ux 2 when the difference concerned is positive, therefore when there is current in one of the phases monitored by the device. [0071] Conversely, when no voltage Ux 2 is obtained as output from the comparison means 17, because of a difference less than or equal to zero between the amplified differential voltage Uxi and the reference value, the absence of current in the phase monitored by the device is deduced therefrom. [0072] The information obtained by the detection means 15 to 17, is also transmitted to computation means, not represented in Figure 3, for processing and use. [0073] In the example of Figure 4, the detection means 21 comprise two comparison means 24, 25. [0074] The function of these two comparison means 24, 25 is also to compare an input voltage value relative to a reference voltage value and to deliver as output a voltage when the difference between this input voltage and the reference voltage is positive.

17 [0075] Specifically, the first comparison means 24 measures the difference between, on the one hand, the voltage between a first of the terminals of the power supply means 19 and a first of the terminals of the rectifying means 18, and, on the other hand, a reference voltage, and delivers as output a voltage when this difference is positive. [0076] Moreover, the second comparison means 25 measures the difference between, on the one hand, the voltage between a second of the terminals of the power supply means 19 and a second of the terminals of the rectifying means 18, and, on the other hand, a reference voltage, and delivers as output a voltage when this difference is positive. [0077] In this variant, the detection means 21 also comprise a logic module 26, or logic gate 26, with two inputs, added at the output of the two comparison means 24, 25. This logic gate 26 delivers an output signal when it receives a signal on at least one of its two inputs. [0078] Thus, the logic gate 26 delivers an output voltage when at least one of the two comparison means 24, 25 delivers an output voltage. [0079] The information thus obtained by the detection means 21 is also transmitted to computation means 23 for processing and use. [0080] It is for example possible to switch the corresponding electronic circuit to standby, based on the presence or absence of a voltage at the output of the logic gate 26. In effect, if neither of the two comparison means 24, 25 delivers an output voltage, this means that there is no current consumption or a very low current consumption, and that the corresponding electronic circuit can be switched to standby. [0081] In this way, it is possible to monitor the state of the corresponding protection circuit 2 to 7 by detecting the absence of current in this protection 18 circuit 2 to 7 via detection means 15 to 17 or 20 described previously, with reference to Figures 2 and 3, which are inserted into the power supply circuit 14 of a device 8 to 13 for measuring the electrical energy distributed to one of the branches A to F of the network. [0082] This detection of the absence of current in the corresponding protection circuit 2 to 7 is obtained by the measurement of the voltage at the terminals of the power supply circuit 14 by the detection means 15 to 17. [0083] Also, it is possible to monitor the state of the corresponding electrical circuit 2 to 7 by detecting the presence of current in this circuit 2 to 7 via detection means 21 described previously, with reference to Figure 4, which are inserted into the power supply circuit 14 of a device 8 to 13 for measuring the electrical energy distribution to one of the branches A to F of the distribution circuit. [0084] This detection of the presence of current in the corresponding power supply circuit 2 to 7 is obtained by the measurement of the voltage at the terminals of the power supply circuit 14 by the detection means 21. [0085] Figures 5 to 7 show different measurements performed on the monitoring device in the variant of Figure 3, to illustrate the detection of the absence of primary current in the power supply circuit 14, therefore in the monitored protection circuit 2 to 7. [0086] More specifically, interest is focused on a monitoring device comprising a measurement device 8 to 13 with a power supply sensor 14 according to the invention, and a conventional power supply sensor. [0087] The case of Figure 5 corresponds to the case of a low primary current in the power supply circuit or sensor 14, namely a primary current of 0.1 A, and a primary current of 10 A in the other power supply circuit or sensor.

19 [0088] The curve identified by the labels C1 shows the charge of the capacitor C1 mentioned above (not represented in the figures). [0089] The sinusoidal curve identified by the labels U, 1 shows the voltage at the output of the differential amplification means 16. [0090] The curve identified by the label S shows the threshold of the comparator used in the comparison means 17. [0091] Finally, the curve identified by the labels U, 2 shows the voltage at the output of the comparison means 17. This voltage U, 2 is non-zero, and reflects the presence of the primary current of 0.1 A in the power supply circuit 14. [0092] Figure 5 shows a limit case of operation. It can thus be seen that it is possible to discriminate a primary current greater than or equal to 0.1 A from a zero current. [0093] The case of Figure 6 corresponds to the case of a relatively high primary current in the power supply circuit or sensor 14, namely a primary current of 600 A, and a primary current of 10 A in the other power supply circuit or sensor. [0094] In this case, since the primary current in the power supply circuit 14 is greater than in the case of Figure 3, the charging of the capacitor C1 is faster as the curve identified by the labels C1 shows. [0095] Moreover, the output voltage U, 1 of the differential amplification means 16 is saturated, as can be seen on the curve identified by the labels Ux. [0096] The curve identified by the label S, corresponding to the threshold of the comparator used in the comparison means 17, is unchanged relative to the case of Figure 3.

20 [0097] The curve identified by the labels Ux 2 shows the voltage at the output of the comparison means 17. This voltage U, 2 is non-zero, and reflects the presence of the primary current of 600 A in the power supply circuit 14. [0098] The case of Figure 7 corresponds to the case of the absence of a primary current in the power supply circuit or sensor 14 (primary current of 0 A), and a primary current of 10 A in the other power supply circuit or sensor. [0099] In this case, it can be seen that a charging of the capacitor C1 takes place despite the absence of primary current in the power supply circuit or sensor 14, as shown by the curve identified by the labels C1, because of the current delivered by the other power supply sensors. [00100] However, since there is no primary current, the output voltage U, 1 of the differential amplification means 16 and the output voltage U, 2 of the comparison means 17 are zero, as can be seen on the curves identified respectively by the labels U, 1 and by the labels U, 2 . [00101] The curve identified by the label S still corresponds to the threshold of the comparator used in the comparison means 17, and therefore remains unchanged relative to the cases of Figures 5 and 6. [00102] The present description is given by way of example and is in no way limiting on the invention.

Claims (18)

1. Monitoring device intended to check the state of an electrical circuit (2 to 7) supplied with electrical energy by an electrical energy source (1), such as an electrical circuit (2 to 7) for protection against electrical overloads of the type comprising at least one fuse (2 to 7) and with which an output of the electrical energy source (1) in an electrical distribution network is equipped, or such as an electrical power supply circuit (2 to 7) for an electronic apparatus at the output of the electrical energy source (1), said monitoring device comprising means (8 to 13) for measuring at least one electrical quantity, such as the electrical energy, associated with the electrical circuit (2 to 7) supplied by the electrical energy source (1), said measurement means (8 to 13) comprising at least one power supply circuit (14) suitable for generating an electrical power supply current and at least one measurement circuit, for example of Rogowski type, suitable for measuring said electrical quantity associated with said power supply circuit (14), characterized in that the power supply circuit (14) comprises detection means (15 to 17, 20, 21) suitable for detecting the absence or the presence of current in the electrical circuit (2 to 7) by measuring the voltage at the terminals of the power supply circuit (14).

2. Device according to claim 1, characterized in that the power supply circuit (14) comprises power supply means (19) and rectifying means (18), such as a Graetz bridge (18), suitable for rectifying the current delivered by the power supply means (19), and in that the detection means (15 to 17, 20, 21) are arranged between the power supply means (19) and the rectifying means (18).

3. Device according to claim 2, characterized in that the detection means (15 to 17) comprise two resistor bridges (15) in parallel between the power supply means (19) and the rectifying means (18), and a differential amplification means (16), and in that the two resistor bridges (15) are linked to the differential amplification means (16) so as to make it possible to amplify the difference 22 between the voltage in one (R7, R8) of the two resistor bridges (15) and the voltage in the other (R9, R14) of these two resistor bridges (15).

4. Device according to claim 3, characterized in that each of the two resistor bridges (15) comprises two resistors (R7, R8, R9, R14), and is linked to one of the two inputs (dif-, dif+) of the differential amplification means (16) by a link point (dif-, dif+) situated between said two resistors (R7, R8, R9, R14).

5. Device according to either one of claims 3 and 4, characterized in that the detection means (15 to 17) comprise a comparison means (17) suitable for comparing an input voltage value relative to a reference voltage value and for delivering as output a voltage when the difference between this input voltage and the reference voltage is positive, and in that the output voltage of the differential amplification means (16) is linked to the input of the comparison means (17), such that the comparison means (17) delivers as output a voltage when the difference between the output voltage of the differential amplification means (16) and the reference voltage is positive.

6. Device according to claim 2, characterized in that the detection means (20) comprise at least one comparison means (24) suitable for comparing an input voltage value relative to a reference voltage value and for delivering as output a voltage when the difference between this input voltage and the reference voltage is positive, and in that the voltage between one of the terminals of the power supply means (19) and one of the terminals of the rectifying means (18) is linked to the input of the comparison means (24), such that the comparison means (24) delivers as output a voltage when the difference between the voltage between said terminal of the power supply means (19) and said terminal of the rectifying means (18) and the reference voltage is positive.

7. Device according to claim 2, characterized in that the detection means (21) comprise at least two comparison means (24, 25) each suitable for 23 comparing an input voltage value relative to a reference voltage value and for delivering as output a voltage when the difference between this input voltage and the reference voltage is positive, and in that the voltage between a first of the terminals of the power supply means (19) and a first of the terminals of the rectifying means (18) is linked to the input of a first (24) of the comparison means (24, 25), and in that the voltage between a second of the terminals of the power supply means (19) and a second of the terminals of the rectifying means (18) is linked to the input of a second (25) of the comparison means (24, 25), such that the first and second comparison means (24, 25) respectively deliver as output a voltage when the difference between the voltage between the first, respectively the second, of the terminals of the power supply means (19) and the first, respectively the second, of the terminals of the rectifying means (18) and the reference voltage is positive.

8. Device according to claim 7, characterized in that the detection means (21) comprise a logic gate (26) with two inputs respectively linked to the output voltages of the two comparison means (24, 25), and suitable for delivering an output voltage when at least one of the two comparison means (24, 25) delivers an output voltage.

9. Electrical energy distribution network comprising a number of branches (A to F) and an electrical energy source (1) suitable for delivering as output electrical energy for each branch (A to F), at least one of the outputs of the electrical energy source (1) being equipped with an electrical circuit (2 to 7) for protection against electrical overloads of the type comprising at least one fuse (2 to 7), characterized in that it comprises, for at least said output of the electrical energy source (1), a monitoring device according to any one of claims 1 to 6, so as to make it possible to detect the absence of current in the electrical circuit (2 to 7) protecting said output of the electrical energy source (1).

10. Distribution network according to claim 9, characterized in that the electrical energy source (1) is suitable for delivering as output three-phase 24 electrical energy for at least one of the branches (A to F) of the distribution network.

11. Electrical energy distribution circuit in an electronic apparatus, comprising an electrical power supply circuit (2 to 7) and an electrical energy source (1) suitable for delivering as output electrical energy to the electrical power supply circuit (2 to 7), characterized in that it comprises a monitoring device according to any one of claims 1, 2, 7 and 8, so as to make it possible to detect the presence of current in the electrical power supply circuit (2 to 7).

12. Method for monitoring the state of an electrical circuit (2 to 7) supplied with electrical energy by an electrical energy source (1), such as an electrical circuit (2 to 7) for protection against electrical overloads of the type comprising at least one fuse (2 to 7) and with which an output of the electrical energy source (1) in an electrical energy distribution network is equipped, or such as an electrical power supply circuit (2 to 7) for an electronic apparatus at the output of the electrical energy source (1), by means of a monitoring device comprising means (8 to 13) for measuring at least one electrical quantity, such as the electrical energy, associated with the electrical circuit (2 to 7), said measurement means (8 to 13) comprising at least one power supply circuit (14) suitable for generating an electrical power supply current and at least one measurement circuit, for example of Rogowski type, suitable for measuring said electrical quantity associated with said power supply circuit (14), characterized in that it comprises a step of detection of the absence or of the presence of current in the electrical circuit (2 to 7) by the measurement of the voltage at the terminals of the power supply circuit (14) by detection means (15 to 17, 20, 21).

13. Method according to claim 12, the power supply circuit (14) comprising two resistor bridges (15) arranged between power supply means (19) and rectifying means (18), such as a Graetz bridge (18), characterized in that the measurement of the voltage at the terminals of the power supply circuit (14) comprises the amplification, by a differential amplification means (16), of the 25 difference between the voltage in one (R7, R8) of the two bridges (15) and the voltage in the other (R9, R14) of the two bridges (15).

14. Method according to claim 13, characterized in that the measurement of the voltage at the terminals of the power supply circuit (14) comprises the comparison, by a comparison means (17), of the differential voltage amplified by the differential amplification means (16) relative to a reference value, and the supply of an output voltage by the comparison means (17) when the amplified differential voltage at the input is greater than the reference voltage.

15. Method according to claim 12, the power supply circuit (14) comprising power supply means (19) and rectifying means (18), such as a Graetz bridge (18), characterized in that the measurement of the voltage at the terminals of the power supply circuit (14) comprises the comparison, by a comparison means (24), of the voltage value between one of the terminals of the power supply means (19) and one of the terminals of the rectifying means (18), and the supply of an output voltage by the comparison means (24) when the difference between the voltage between said terminal of the power supply means (19) and said terminal of the rectifying means (18) and the reference voltage is positive.

16. Method according to claim 12, the power supply circuit (14) comprising power supply means (19) and rectifying means (18), such as a Graetz bridge (18), characterized in that the measurement of the voltage at the terminals of the power supply circuit (14) comprises the comparison, by a first comparison means (24), of the voltage value between a first of the terminals of the power supply means (19) and a first of the terminals of the rectifying means (18), the comparison, by a second comparison means (25), of the voltage value between a second of the terminals of the power supply means (19) and a second of the terminals of the rectifying means (18), and the supply of a respective output voltage by the first and second comparison means (24, 25) when the difference between the voltage between the first, respectively the second, of the terminals of 26 the power supply means (19) and the first, respectively the second, of the terminals of the rectifying means (18) and the reference voltage is positive.

17. Method according to claim 16, characterized in that the measurement of the voltage at the terminals of the power supply circuit (14) comprises the supply, by a logic gate (26) with two inputs linked respectively to the output voltages of the two comparison means (24, 25), of an output voltage when at least one of the two comparison means (24, 25) delivers an output voltage.

18. Method according to claim 17, the monitored electrical circuit (2 to 7) being a power supply circuit of an electronic apparatus, characterized in that it comprises the switching of the electronic apparatus to standby based on the absence of voltage at the output of the logic gate (26). SCHNEIDER ELECTRIC INDUSTRIES SAS WATERMARK PATENT AND TRADE MARKS ATTORNEYS P41082AU00