Detecting open or closed state of a circuit breaker

Abstract

A meter (1) comprising a phase conductor (10) connected to a phase line of a network, a disconnecting member (12) and a detection circuit, comprising: an injection chain (15) arranged to generate a test signal (St) having a predetermined voltage level when the disconnecting member is open, and arranged to inject the test signal into the phase conductor downstream of the disconnecting member; a measurement chain (16) arranged to measure an intermediate voltage level of the test signal at a measurement point (Pm) of the injection chain, the point being located between the generator assembly and the injection assembly; a processor assembly (17) arranged to act on the intermediate voltage level in order to determine whether the circuit breaker is open or closed.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of electricity meters. BACKGROUND

[0002] Modern electricity meters are electronic instruments called "smart", which are of course designed to measure the electrical energy delivered to an electrical installation by a distribution party via a distribution network, but which are also able to perform a certain number of additional functions: reception of instructions to manage taxes, remote meter reading and programming, customer information, etc.

[0003] Some electricity meters comprise a cut-off device (located inside the meter) which makes it possible to operate it remotely or from the meter itself, in order to selectively connect and disconnect the electrical installation to the distribution network. The cut-off component is used in particular to remotely interrupt or re-establish the electrical power supply to the installation, for example in the event of cancellation of a subscription or non-compliance with a subscription contract.

[0004] The electrical installation itself is also often equipped with a circuit breaker, which is located outside the meter and downstream of the meter (i.e. on the installation side of the meter). The subscriber-actuable circuit breaker is used in particular to protect the subscriber's electrical installation by opening in the event of a surge in the distribution network, for example caused by a short circuit between two phases or between one of these phases and the neutral.

[0005] In certain countries, the subscriber is required to open and then re-close the circuit breaker after the cut-off component has opened, before the cut-off component re-closes.

[0006] In order to be able to automatically re-establish the electrical power supply to the subscriber, it is advantageous for the meter to be able to detect whether the circuit breaker is open or closed at the time when the cut-off component opens.

[0007] In order to perform this detection, it has been proposed to deliver a portion of the voltage present on the network to a point downstream of the cut-off component, and to "amplify" the resulting voltage by means of an adjustable voltage divider, in order to accurately measure the impedance present downstream of the meter. This system serves to distinguish between an open circuit breaker and a closed circuit breaker (and in particular a closed circuit breaker on a node which is very small and therefore presents a high impedance). This detection system is therefore relatively effective, but it requires measurements to be made at very low voltage levels (a few millivolts (mV)) in order to distinguish between the open and closed states of the circuit breaker. This detection system is therefore relatively sensitive to noise.

[0008] OBJECT OF THE INVENTION

[0009] The object of the present invention is to act from inside the meter in a reliable and robust manner in order to detect the open or closed state of the circuit breaker at the time when the cut-off component opens. SUMMARY

[0010] To achieve this object, there is provided a meter arranged to measure electrical energy delivered to a facility through an electricity distribution network having a phase line and a neutral line, the meter being arranged to be connected to a circuit breaker located outside the meter and downstream of the meter, the meter comprising:

[0011] • a phase conductor and a neutral conductor arranged to be connected to the phase line and the neutral line of the electricity distribution network, respectively;

[0012] • a cut-off component connected in the phase conductor;

[0013] • a detection circuit comprising:

[0014] an injection chain comprising at least one generator assembly arranged to generate a test signal having a predetermined voltage level when the cut-off component is open, and an injection assembly arranged to inject the test signal into the phase conductor downstream of the cut-off component;

[0015] a measurement chain arranged to measure an intermediate voltage level of the test signal at a measurement point of the injection chain, the point being located between the at least one generator assembly and the injection assembly;

[0016] a processor assembly arranged to act on the intermediate voltage level in order to determine whether the circuit breaker is open or closed.

[0017] By injecting the test signal into the phase conductor, the detection circuit of the meter of the present invention makes it possible to detect whether the circuit breaker is open or closed when the cut-off component is open.

[0018] The level difference of the intermediate voltage between the open and closed states of the circuit breaker is typically of the order of 1 volt (V) or about 100 mV, and it is therefore easy to measure. The detection is less sensitive to noise, and it is therefore more reliable and more robust than the prior art.

[0019] There is also provided a meter as described above, the injection assembly being a first capacitor integrated in a first high-pass filter for filtering out interference signals from the electricity distribution network.

[0020] There is also provided a meter as described above, wherein the at least one generator assembly comprises both a generator module arranged to generate the test signal having the predetermined voltage level and a driver forming a current source arranged to ensure that the test signal is generated with a current level sufficient to maintain at the output of the at least one generator assembly a voltage level equal to the predetermined voltage level.

[0021] There is also provided a meter as described above, wherein the measurement chain comprises, in order from upstream to downstream, a second high-pass filter, an envelope detector and a low-pass filter.

[0022] There is also provided a meter as described above, further comprising an analog-to-digital converter upstream of the envelope detector.

[0023] There is also provided a meter as described above, further comprising an analog-to-digital converter downstream of the envelope detector.

[0024] There is also provided a meter as described above, the injection chain being arranged to inject the test signal periodically for a predetermined duration when the disconnecting component is open.

[0025] There is also provided a meter as described above, the injection chain being arranged to inject the test signal continuously when the disconnecting component is open.

[0026] There is also provided a meter as described above, wherein the test signal is an alternating signal at a frequency at least one hundred times greater than a frequency of a phase current flowing in a phase line of the electrical distribution network.

[0027] There is also provided a meter as described above, the meter being a single-phase meter.

[0028] There is also provided a meter as described above, wherein the phase conductor is connected to an electrical ground of the meter upstream of the disconnecting component, the meter further comprising a second capacitor upstream of the disconnecting component and having a first terminal connected to the neutral conductor and a second terminal connected to the phase conductor.

[0029] There is also provided a meter as described above, the injection assembly being a first capacitor, the injection chain comprising a resistor connected between the first capacitor and an output of the at least one generator assembly, the processor assembly being arranged to compare an intermediate voltage level of the test signal to a predetermined detection threshold, and to detect that the circuit breaker is open when the intermediate voltage level of the test signal is greater than the predetermined threshold, and to detect that the circuit breaker is closed when the intermediate voltage level of the test signal is less than or equal to the predetermined detection threshold, the predetermined detection threshold being located between a high level and a low level Vb, such that:

[0030] Vb = Vp * (Z(C1) + Z(subscriber) + Z(C2) || Z(upstream)) / (R + Z(C1) + Z(subscriber) + Z(C2) || Z(upstream)), where:

[0031] (R + Z(C1) + Z(subscriber) + Z(C2) || Z(upstream)), where:

[0032] Vp is a predetermined voltage level, Z(C1) is an impedance of the first capacitor, Z(C2) is an impedance of the second capacitor, Z(upstream) is an impedance between the phase line and the neutral line upstream of the meter, Z(subscriber) is an impedance between the phase line and the neutral line downstream of the meter, the impedance being estimated at a frequency of the test signal.

[0033] There is also provided a meter as described above, the meter being a three-phase meter. There is also provided a meter as described above, the injection assembly being a first capacitor, the injection chain comprising a resistor connected between the first capacitor and an output of the at least one generator assembly, the processor assembly being arranged to compare the mid voltage level of the test signal to a predetermined detection threshold, and to detect that the circuit breaker is open when the mid voltage level of the test signal is greater than the predetermined threshold, and to detect that the circuit breaker is closed when the mid voltage level of the test signal is less than or equal to the predetermined detection threshold, the predetermined detection threshold being located between the high level and the low level Vb, such that:

[0034] Vb = Vp * (Z(C1) + Z(subscriber)) / (R + Z(C1) + Z(subscriber)), where:

[0035] Vp is a predetermined voltage level of the test signal, Z(C1) is the impedance of the first capacitor, and Z(subscriber) is the impedance between the phase line and the neutral line downstream of the meter, the impedance being estimated at the frequency of the test signal.

[0036] There is also provided a detection method performed in the processor assembly of a meter as described above, the method comprising the following steps performed when the disconnecting member is open:

[0037] • using the injection chain and generating a test signal and injecting the test signal into the phase conductor downstream of the disconnecting member;

[0038] • acquiring a mid voltage level of the test signal;

[0039] • determining whether the circuit breaker is open or closed depending on the mid voltage level of the test signal.

[0040] There is also provided a computer program comprising instructions causing the processor assembly of a meter as described above to perform the steps of the above detection method.

[0041] There is also provided a computer-readable storage medium storing the above computer program.

[0042] The present application can be better understood in light of the following description of specific non-limiting embodiments of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0043] With reference to the drawings, in which:

[0044] [ Figure 1 ] Figure 1 An electricity meter in a first embodiment of the present application is shown, the electricity meter being a single-phase meter;

[0045] [ Figure 2 ] Figure 2 An electricity meter in a second embodiment of the present application is shown, the electricity meter being a three-phase meter. DETAILED DESCRIPTION

[0046] REFERENCE Figure 1 The electricity meter 1 in the first embodiment of the application is a single-phase meter for measuring the energy supplied by the electricity distribution network 3 to the electrical installation 2 of a subscriber.

[0047] The electricity distribution network 3 comprises a phase line 4 and a neutral line 5.

[0048] The circuit breaker 6 is located outside the meter 1 and downstream thereof. In this description, when referring to the position of various elements relative to the installation 2 and the network 3, the following terminology convention is used:

[0049] • "upstream": on the network 3 side;

[0050] • "downstream": on the installation 2 side.

[0051] The circuit breaker 6 is positioned between the meter 1 and the installation 2.

[0052] The meter 1 has an upstream phase port P connected to the phase line 4 and an upstream neutral port N connected to the neutral line 5. The meter 1 also has a downstream phase port P' and a downstream neutral port N'.

[0053] The downstream phase port P' and the downstream neutral port N' of the meter 1 are connected to the installation 2 via respective switches 8 and 9 both of which are integrated in the circuit breaker 6.

[0054] The meter 1 also has a phase conductor 10 connected to the phase line 4 of the electricity distribution network 3 via the upstream phase port P and connected to the circuit breaker 6 via the downstream phase port P'. The meter 1 also has a neutral conductor 11 connected to the phase line 5 via the upstream neutral port N and connected to the circuit breaker 6 via the downstream phase port N'.

[0055] The meter 1 also comprises a cut-off component 12 comprising a switch 13 connected in the phase conductor 10.

[0056] The instrument 1 also has an electrical ground 14. The phase conductor 10 is connected to the ground 14 near the upstream phase port P and upstream of the cut-off component 12. This grounding of the phase conductor 10 is explained by the fact that the instrument 1 comprises a current sensor for measuring the phase current flowing in the phase line 4, this sensor being a shunt (not shown) located in the phase conductor 10 upstream of the cut-off component 12. If the phase conductor 10 were not grounded, the voltage at the terminals of the shunt would be of the same order of magnitude as the voltage existing between the phase line and the neutral line of the network 3 and would thus be very high. Grounding the phase conductor 10 serves to obtain a low voltage at the terminals of the shunt (of the order of 3.3 V after application of a gain in this example, it being understood that the voltage at the terminals of the shunt is of the order of 15 mV to 20 mV when passing through a root mean square (RMS) current of 100 amperes (A)), which corresponds to an acceptable voltage range as input for a metering microcontroller (not shown) integrated in the instrument 1.

[0057] The instrument 1 also comprises a detection circuit.

[0058] The detection circuit comprises an injection chain 15, a measurement chain 16 and a processor assembly.

[0059] In this description, the term “chain” is used to denote a sequence of one or more assemblies (or functional modules) connected in series.

[0060] The injection chain 15 comprises at least one generator assembly (in this example specifically two generator assemblies), a resistor R and an injection assembly (in this example specifically a first capacitor C1).

[0061] The two generator assemblies comprise a generator module 20 integrated in an application microcontroller 17 of the instrument 1 and a driver 21.

[0062] The microcontroller 17 has a pulse width modulation (PWM) output 22. The output of the generator module 20 is connected to the PWM output 22.

[0063] In this example, the driver 21 is connected as a voltage follower amplifier. The output 22 of the microcontroller 17 is connected to the non-inverting input of the driver 21. The inverting input of the driver 21 is connected to the output of the driver 21.

[0064] The output of the driver 21 is connected to a first terminal of the resistor R, a second terminal of the resistor R being connected to a first terminal of the first capacitor C1. A second terminal of the first capacitor C1 is connected to the phase conductor 10 downstream of the cut-off component 12.

[0065] In this example, the resistor R presents a resistance equal to 1 kilo-ohm (kΩ). In the equations here, “R” is also used to denote the impedance of the resistor R.

[0066] In this example, the first capacitor C1 has a capacitance of 47 nanofarads (nF). The first capacitor C1 is integrated into a first high-pass filter (R-C1 filter) for filtering out interference signals from the distribution network 3.

[0067] The measurement chain 16 includes the following components arranged sequentially from upstream to downstream: a second high-pass filter 24, an analog-to-digital converter (ADC) 25, an envelope detector 26, and a low-pass filter 27.

[0068] In this specification, when referring to the relative positions of the various elements in the measuring chain 16, the following terminology conventions are used:

[0069] • "Upstream": On the side of the quantity to be measured;

[0070] • "Downstream": On the measurement and processing side.

[0071] In this example, the second high-pass filter 24 is therefore an analog filter, while the envelope detector 26 and the low-pass filter 27 are digital modules.

[0072] In this example, the ADC 25, envelope detector 26, and low-pass filter 27 are integrated into the microcontroller 17.

[0073] In this example, the processor component of the detection circuit is a microcontroller 17.

[0074] The microcontroller 17 is adapted to execute program instructions for performing the detection method described below. This program is stored in a memory 28, which is integrated into or connected to the microcontroller 17.

[0075] Instrument 1 also includes a second capacitor C2 located upstream of the disconnecting component 12, having a first terminal connected to the neutral conductor 11 and a second terminal connected to the phase conductor 10. The capacitance of the second capacitor C2 is typically equal to the capacitance of the first capacitor C1, i.e., 47 nF in this example. Positioned in this manner between the neutral conductor 11 and the phase conductor 10, the second capacitor C2 serves to form a controlled ground return path during detection measurements (it should be recalled that these measurements are performed when the disconnecting component 12 is open).

[0076] The following describes in detail how the present invention operates.

[0077] When the cutting component 12 is open, the injection chain 15 periodically injects the test signal St over a predetermined duration. By way of example, the period is equal to 1 second (s) and the predetermined duration is equal to 500 milliseconds (ms), that is, when the cutting component 12 is closed, the test signal St is injected for 500 ms, and this is done once per second.

[0078] Alternatively, when the cut-off component 12 is disconnected, the injection chain 19 can inject the test signal St continuously.

[0079] To perform this injection, the generator module 20 of the microcontroller 17 generates the test signal St and applies it to the output 22.

[0080] In this example, the test signal St is a square (or rectangular) wave signal alternating at a frequency which is advantageously at least 100 times greater than the frequency of the phase current flowing in the phase line 4 of the electricity distribution network 3.

[0081] In this example, the frequency of the phase current is equal to 50 Hertz (Hz) and the frequency of the test signal St is equal to 10 kilohertz (kHz).

[0082] The test signal St is generated by the microcontroller 17 at a predetermined voltage level which, in this example, is equal to 3.3 V (peak to peak).

[0083] The test signal St is applied to the non-inverting input of the driver 21 and is thus reproduced at the output of the driver 21.

[0084] The driver 21 forms a current source supplying an additional current which serves to ensure that the test signal St is generated with sufficient current to ensure that the voltage level at the output of the generator assembly (i.e. at the output of the driver 21) is at the predetermined voltage level. In this example, the driver 21 is necessary because the various elements making up and connected to the injection chain 15 “draw” more current than the microcontroller 17 is able to deliver itself.

[0085] The resistor R serves to limit the current.

[0086] The first capacitor C1 serves to inject the test signal St generated by the microcontroller 17 and the driver 21 into the phase conductor 10 downstream of the cut-off component 12.

[0087] The measurement chain 16 serves to measure the intermediate voltage level of the test signal St at a measurement point Pm of the injection chain 15, this point being located between at least one generator assembly and the injection assembly.

[0088] In this example, the measurement point Pm is located between the resistor R and the first capacitor C1.

[0089] In this example, the second high-pass filter 24 is an active high-pass filter with a gain of 1. The cutoff frequency of the second high-pass filter 24 is typically equal to 5 kHz. Located upstream of the ADC 25, the second high-pass filter 24 is used to eliminate any 50 Hz interference (such as that that can be picked up by the antenna effect when both the cut-off component 12 and the circuit breaker 6 are open) and also to eliminate any interference that may come from the network 3. The second high-pass filter 24 is thus used to present the ADC 25 with an undisturbed signal. The envelope of the signal is then sufficiently detected (via the digital envelope detector 26) and the output from the detector 26 is digitally filtered by a low-pass filter 27, which has a cutoff frequency typically equal to 10 Hz.

[0090] The microcontroller 17 compares the intermediate voltage level of the measured test signal St with a predetermined threshold, and determines that the circuit breaker 6 is open when the intermediate voltage level of the test signal St is greater than the predetermined threshold, and determines that the circuit breaker 6 is closed when the intermediate voltage level of the test signal St is less than or equal to the predetermined threshold.

[0091] Specifically, when circuit breaker 6 is open, the signal input to ADC 25 is high.

[0092] In this example, it is assumed that at 10kHz, both the modulus of the load Z(subscriber) and the modulus of the load Z(upstream) are very small compared to the resistance of the resistor R (although this does not necessarily have to be the case, at least for Z(subscriber): see below).

[0093] After low-pass filtering, the measured intermediate voltage level is equal to the high level Vh of 3.3V (that is, equal to the predetermined voltage level Vp of the test signal St).

[0094] Conversely, when circuit breaker 6 is closed, the signal input to ADC 25 is essentially low. After low-pass filtering, the measured intermediate voltage level is equal to the low level Vb, which, through voltage division, equals:

[0095] Vb=Vp*(Z(C1)+Z(Subscriber)+Z(C2)||Z(Upstream) /

[0096] (R+Z(C1)+Z(Subscriber)+Z(C2)||Z(Upstream)), where:

[0097] Z(C1) is the impedance of the first capacitor, Z(C2) is the impedance of the second capacitor, Z(upstream) is the impedance between the phase line and neutral line upstream of instrument 1, and Z(subscriber) is the impedance between the phase line and neutral line downstream of instrument 1. The impedances are estimated at the frequency of the test signal (i.e., 10kHz) and the symbol “||” is used to refer to “in parallel with”.

[0098] The predetermined threshold Sp is thus situated between the high level Vh (equal to the predetermined voltage level Vp in this example) and the low level Vb.

[0099] In this example, the low level is equal to 1.06 V.

[0100] As used in this example, the "ideal" predetermined threshold Sp is thus such that:

[0101] Sp = (Vh + Vb) / 2 = 2.18 V.

[0102] It should be observed that, by default, the PWM output 22 is 0, so that no test signal is injected at the measurement point. Again, this is always the case when the shut-off member 12 is closed.

[0103] Referring to Figure 2 , the meter 101 in the second embodiment of the invention is a three-phase meter. In Figure 2 , each element that is shown and that is similar to the elements in Figure 1 is given reference by adding 100 to the reference in Figure 1 .

[0104] The electricity distribution network 103 has three phase lines 104_i (i ranging from 1 to 3) and a neutral line 105.

[0105] For each phase line 104_i, the meter 101 has a respective upstream phase port Pi and a respective downstream phase port P'i connected to said phase line 104_i.

[0106] The meter 101 also has an upstream neutral port N and a downstream neutral port N' connected to the neutral line 105.

[0107] The downstream phase ports P'i and the downstream neutral port N' of the meter 101 are connected to the installation 102 via switches 108_i and 109 integrated in the circuit breaker 106, respectively.

[0108] For each phase line 104_i, the meter 101 also comprises a respective phase conductor 110_i connected to said phase line 104_i via the associated upstream phase port Pi. The meter 101 also has an upstream neutral conductor 111 connected to the neutral line 105 via the upstream neutral port N.

[0109] The meter 101 also comprises a shut-off member 112, which, for each phase line, comprises a respective switch 113_i connected in the associated phase conductor 110_i.

[0110] The meter 101 also has a detection circuit for detecting whether the circuit breaker 106 is open or closed when the shut-off member 112 is open.

[0111] The four switches 108_i, 109 of the disconnector 106 and the three switches 113_i of the cutout component 112 are either all simultaneously open or all simultaneously closed.

[0112] As a result, in this example, the meter 101 has only one detection circuit which is connected to only one of the phase conductors 110_i (to the Figure 2 Nevertheless, the meter 101 can perfectly have multiple detection circuits in order to confirm the result and thereby improve the robustness of the detection.

[0113] The detection circuit of the meter 101 operates in the same way as the detection circuit of the meter 1.

[0114] The detection circuit has an injection chain 115 comprising a generator module 120 and a driver 121 (two generator components) integrated in an application microcontroller 117, a first capacitor C1 (injection component), and a resistor R connected between the output of the driver 121 and the first capacitor C1. The first capacitor C1 and the resistor R form a first high-pass filter.

[0115] The detection circuit also has a measurement chain 116 comprising a (analog) second high-pass filter 124, an ADN 125, a (digital) envelope detector 126, and a (digital) low-pass filter 127.

[0116] The detection circuit also has a processor component, specifically the microcontroller 117 (with the ADC 125, the envelope detector 126, and the low-pass filter 127 integrated therein).

[0117] It should be observed that, for the three-phase meter 101, for each phase line 104_i, the current sensor for measuring the phase current flowing in said phase line 104_i is a torus and not a shunt. The neutral conductor 105 can thus be connected to the ground (electrical ground 114) visible to the microcontroller 117, so that a second capacitor C2 is not necessary.

[0118] When the cutout component 112 is open, the test signal St is generated and injected in the same way as the detection circuit described above.

[0119] Again, it is assumed that, at 10 kHz, the modulus of the load Z (subscriber) is very small compared to the resistance of the resistor R.

[0120] When the disconnector 106 is open, the measured intermediate voltage level is equal to the high level Vh equal to 3.3 V (i.e. equal to the predetermined voltage level Vp of the test signal St).

[0121] When the breaker 106 is closed, the measured intermediate voltage level is substantially smaller. After low-pass filtering, the measured intermediate voltage level is equal to a low level Vb, which is equal to:

[0122] Vb = Vp * (Z(C1) + Z(subscriber)) / (R + Z(C1) + Z(subscriber)), where:

[0123] Z(C1) is the impedance of the first capacitor and Z(subscriber) is the impedance between the phase and neutral lines downstream of the meter, where said impedance is estimated at the frequency of the test signal (10 kHz in this example).

[0124] The predetermined threshold Sp is thus situated between the high level Vh and the low level Vb.

[0125] In this example, the low level Vb is equal to 1.06 V.

[0126] As used in this example, the "ideal" predetermined threshold Sp is thus such that:

[0127] Sp = (Vh + Vb) / 2 = 2.18 V.

[0128] It should be observed that, in both the single-phase meter 1 and the three-phase meter 101, it is assumed that, at 10 kHz, the modulus of the load Z(subscriber) is very small compared to the resistance of the resistor R.

[0129] However, this "standard" configuration does not necessarily apply.

[0130] The impedance Z(subscriber) does not need to be negligible compared to the resistance of the resistor R, and in fact it can be substantially greater than this resistance, although the impedance Z(upstream) is less than or equal to 2 Ω and is always negligible compared to the resistance of the resistor R.

[0131] This happens, for example, in Spain, where the breaker 6 (or 106) is geographically far from the meter 1 (or 101) in the worst case.

[0132] In such a case, when the breaker is open, the cable between the meter and the breaker imposes an equivalent impedance to the terminals of the meter, which depends on the length and nature of the cable, which can be up to 1200 kΩ.

[0133] When the breaker is closed, in addition to those 1200 kΩ, there is in parallel the impedance Z(subscriber) which can be up to 210 kΩ.

[0134] In this "Spanish type" configuration, in order to improve the difference between the intermediate voltage levels measured at point Pm when the circuit breaker is open (high level Vh) and when the circuit breaker is closed (low level Vb), the resistance and capacitance values of resistor R and capacitor C1 are modified (the capacitance of capacitor C2 remains unchanged at 47 nF).

[0135] By way of example, the following values are chosen: R = 22 kΩ and C1 = 2.2 nF.

[0136] Therefore, in this "Spanish type" configuration, the following intermediate voltage values are obtained, whether single-phase or three-phase (using the above formula):

[0137] • circuit breaker open: Vh = 3.24 V;

[0138] • circuit breaker closed: Vb = 2.94 V;

[0139] which gives the "ideal" predetermined threshold Sp:

[0140] • Sp = 3.09 V.

[0141] Moreover, these "new" values of R and C1 are fully applicable to the "standard" configuration previously described (Z (subscriber) « R and no impedance of 1200 kΩ is applied).

[0142] In the "standard" configuration, the calculated new values of the components are as follows:

[0143] • circuit breaker open: Vh = 3.3 V;

[0144] • circuit breaker closed: Vb = 1.03 V.

[0145] The "ideal" predetermined threshold Sp is therefore such that:

[0146] Sp = 2.17 V.

[0147] It should also be observed that the predetermined threshold Sp, equal to 3.09 V instead of 2.17 V, is compatible with both the "Spanish type" configuration and the "standard" configuration.

[0148] It should also be observed that the 3 decibel (dB) cut-off frequency of the high-pass filter R-C1 remains practically unchanged within 3% when using the values of the "standard" configuration or the values of the "Spanish type" configuration, since it varies from 3386 Hz to 3288 Hz.

[0149] Naturally, the present application is not limited to the described embodiments, but encompasses any variants falling within the scope of the present application as defined by the claims.

[0150] The above described digital envelope detector can equally well be analog and will then be positioned upstream of the ADC.

[0151] The capacitance values of the first capacitor C1 and the second capacitor C2 can differ from those given above. Also, the resistance of the resistor R can typically be changed by increasing it.

[0152] The frequency of the test signal can equally well be modified, which will make it necessary to adapt the predetermined detection threshold to obtain equivalent results. The predetermined detection threshold can be settable.

[0153] A driver is not necessary. In particular, if the generator module (application microcontroller in the above description) that generates the test signal is able to deliver sufficient current, then a driver is not needed.

[0154] The microcontroller that implements the application does not necessarily need to be an application microcontroller, but can be a different component.

[0155] The processor component that implements the application does not necessarily need to be a microcontroller, but can be some other component, for example it can be a conventional processor, a digital signal processor (DSP), or indeed it can be a programmable logic circuit, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC).

Claims

1. An instrument (1; 101) arranged to measure power delivered to a facility (2; 102) by an electricity distribution network (3; 103) comprising a phase line and a neutral line. 102) of the electrical energy, the meter being arranged to be connected to a disconnector (6; 106) located outside the meter and downstream of the meter; • a phase conductor (10; 110_i) and a neutral conductor (11; 111) arranged to be connected to the phase line and to the neutral line, respectively, of the electrical distribution network; • a cut-off component (12; 112) connected in the phase conductor; • a detection circuit comprising: - an injection chain (15; 115) comprising at least one generator assembly arranged to generate a test signal (St) having a predetermined voltage level when the cut-off component is open, and an injection assembly arranged to inject the test signal into the phase conductor downstream of the cut-off component; - a measurement chain (16; 116) arranged to measure an intermediate voltage level of the test signal at a measurement point (Pm) of the injection chain, the measurement point being located between the at least one generator assembly and the injection assembly; - a processor assembly (17; 117) arranged to act on the basis of the intermediate voltage level in order to determine whether the disconnector is open or closed.

2. The meter of claim 1, wherein, The injection assembly is a first capacitor (C1) integrated in a first high-pass filter for filtering out interference signals from the electrical distribution network.

3. An instrument as claimed in any preceding claim, wherein, The at least one generator assembly comprises both a generator module (20; 120) arranged to generate a test signal having a predetermined voltage level and a driver (21; 121) forming a current source arranged to ensure that the test signal is generated with a current level sufficient to maintain at the output of the at least one generator assembly a voltage level equal to the predetermined voltage level.

4. The meter of claim 1, wherein The measurement chain comprises, in succession from upstream to downstream, a second high-pass filter (24; 124), an envelope detector (26; 126) and a low-pass filter (27; 127).

5. The meter of claim 4, wherein, An analog-to-digital converter (25; 125) located upstream of the envelope detector is also included.

6. The meter of claim 4, wherein, An analog-to-digital converter located downstream of the envelope detector is also included.

7. The meter of claim 1, wherein The injection chain is arranged to inject the test signal periodically for a predetermined duration when the cut-off component is open.

8. The meter of claim 1, wherein, The injection chain is arranged to inject the test signal continuously when the cut-off component is open.

9. The meter of claim 1, wherein The test signal is an alternating signal at a frequency at least one hundred times greater than the frequency of the phase current flowing in the phase line of the electrical distribution network.

10. The meter of claim 1, wherein, The meter is a single-phase meter (1).

11. The meter of claim 10, wherein, The phase conductor is connected to an electrical ground (14) of the meter upstream of the cut-off component, the meter further comprising a second capacitor (C2) located upstream of the cut-off component and having a first terminal connected to the neutral conductor and a second terminal connected to the phase conductor.

12. The meter of claim 11, wherein, the injection chain comprises a resistor connected between the first capacitor and an output of the at least one generator assembly, the processor assembly is arranged to compare the intermediate voltage level of the test signal to a predetermined detection threshold, and to detect that the disconnection means is open when the intermediate voltage level of the test signal is greater than the predetermined detection threshold, and to detect that the disconnection means is closed when the intermediate voltage level of the test signal is less than or equal to the predetermined detection threshold, the predetermined detection threshold being located between a high level and a low level Vb, such that: Vb = Vp * (Z(C1) + Z(subscriber) + Z(C2) || Z(upstream) / (R + Z(C1) + Z(subscriber) + Z(C2) || Z(upstream)), where: Vp is the predetermined voltage level, Z(C1) is the impedance of the first capacitor, Z(C2) is the impedance of the second capacitor, Z(upstream) is the impedance between the phase and neutral lines upstream of the meter, Z(subscriber) is the impedance between the phase and neutral lines downstream of the meter, the impedances being estimated at the frequency of the test signal, and R is the impedance of the resistor.

13. The meter of claim 1, wherein, the meter is a three-phase meter (101).

14. The meter of claim 13, wherein, the injection chain comprises a resistor connected between the first capacitor and an output of the at least one generator assembly, the processor assembly is arranged to compare the intermediate voltage level of the test signal to a predetermined detection threshold, and to detect that the disconnection means is open when the intermediate voltage level of the test signal is greater than the predetermined detection threshold, and to detect that the disconnection means is closed when the intermediate voltage level of the test signal is less than or equal to the predetermined detection threshold, the predetermined detection threshold being located between a high level and a low level Vb, such that: Vb = Vp * (Z(C1) + Z(subscriber) + Z(C2) || Z(upstream) / (R + Z(C1) + Z(subscriber) + Z(C2) || Z(upstream)), where: Vp is the predetermined voltage level, Z(C1) is the impedance of the first capacitor, Z(C2) is the impedance of the second capacitor, Z(upstream) is the impedance between the phase and neutral lines upstream of the meter, Z(subscriber) is the impedance between the phase and neutral lines downstream of the meter, the impedances being estimated at the frequency of the test signal, and R is the impedance of the resistor.

15. A detection method performed in a meter as claimed in any preceding claim, the method comprising the following steps performed when the disconnection means is open: • using the injection chain to generate and inject the test signal into the phase conductor downstream of the disconnection means; • acquiring the intermediate voltage level of the test signal; • determining whether the disconnection means is open or closed from the intermediate voltage level of the test signal.

16. A computer program product comprising instructions for causing a meter as claimed in any of claims 1 to 14 to perform the steps of the detection method as claimed in claim 15.

17. A computer-readable storage medium having stored the computer program product as claimed in claim 16.

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