Electricity meter including a power relay and method for monitoring the power relay of an electricity meter
A real-time resistance estimation method using current and voltage sensors in electricity meters accurately detects abnormal heating, addressing imprecision in temperature-based monitoring and preventing fires.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- SAGEMCOM ENERGY & TELECOM SAS
- Filing Date
- 2024-12-18
- Publication Date
- 2026-06-19
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
Title of the invention: Electricity meter comprising a power relay and method for monitoring the power relay of an electricity meter technical field
[0001] The various embodiments described in this disclosure relate to an electricity meter comprising a power relay intended to be connected upstream to an electrical network and downstream to an installation. They also relate to a method for monitoring the power relay of such an electricity meter. Background
[0002] An electricity meter typically includes a power relay that can be closed or opened to manage the connection between an electrical network and an electrical installation. This power relay can overheat, for example, in the case of a high current. An extreme temperature in the power relay can cause the meter to catch fire.
[0003] It is known in the prior art to monitor the temperature in the meter and generate alerts when it exceeds a certain threshold. These methods depend on the external temperature and are therefore imprecise.
[0004] There is a need for a monitoring method that allows for more precise detection of abnormal power relay temperatures. Summary
[0005] The independent claims define several aspects of this disclosure. Furthermore, other aspects or embodiments are defined in the dependent claims.
[0006] A first aspect of this disclosure relates to a method for monitoring an electrical device intended to be mounted between the electrical grid and an electrical installation. The electrical grid delivers a single-phase or multi-phase electrical signal. The electrical device described herein comprises at least:
[0007] - for each phase, a current sensor mounted in series with a power relay and intended to measure a current flowing in the power relay when it is closed, the current sensor being intended to be connected to the electrical network at an upstream point and the power relay being intended to be connected to the installation at a downstream point,
[0008] - for each phase, a first voltage sensor mounted at the upstream point to to measure upstream voltage,
[0009] - for each phase, a second voltage sensor mounted at the downstream point to measure downstream tension,
[0010] - at least one analog-to-digital converter, configured to obtain, for each phase, at a plurality of measurement times over one or more measurement periods, samples of the upstream voltage, downstream voltage and current, and
[0011] - a transmission modem.
[0012] The method for monitoring the device comprises at least the following steps:
[0013] - a determination, for each phase, from the samples obtained, of quantities whose ratio is representative of a resistance value of the power relay for the measurement period,
[0014] - an alert generation based on the report obtained, and
[0015] - an alert transmission via the transmission modem.
[0016] The monitoring method estimates the contact resistance value of the power relay in real time to detect abnormal heating of the power relay that could lead to a flame and potentially cause a fire. It allows an alarm to be triggered before the fire risk becomes too critical. It also allows the electrical meter of an installation to be exonerated in the event of a fire (if the estimated resistance value of the power relay is low, this proves that the meter is not the cause of the fire).
[0017] One advantage of this monitoring method is that it does not use temperature measurement. The results obtained are more accurate than those obtained with temperature measurements and are independent of the outside temperature. Another advantage is that the method can be implemented in any electrical device or electricity meter since it uses measurements and calculations that can be performed using standard electronic components and software. The method can be implemented by computer. Meters already installed in the network can be remotely updated to a software version suitable for implementing the method.
[0018] In a first embodiment of the monitoring method, the upstream voltage, downstream voltage, and current samples are obtained from the same analog-to-digital converter. The method then comprises:
[0019] - a determination, for each measurement instant of each measurement period, of a difference between a first function of the upstream voltage samples and a second function of the downstream voltage samples,
[0020] - an integration of the differences determined over each measurement period, for to obtain a first representative value of the voltage across the power relay for each measurement period,
[0021] - an integration of a third function of the current samples on each measurement period, to obtain a second quantity representative of the current flowing in the power relay for each measurement period,
[0022] - a calculation of a ratio between the first and second quantity, or between a average of the first and an average of the second quantities, to obtain the resistance value of the power relay for the measurement period(s).
[0023] This embodiment is particularly precise but requires that the samples be obtained by the same analog-to-digital converter, the samples must be synchronous to calculate said difference.
[0024] In some cases, particularly for certain meters in the existing fleet, the samples are obtained from several analog-to-digital converters, typically a first converter (for example, with a 24-bit resolution) to obtain the upstream voltage and current samples, and a second converter (for example, with a 12-bit resolution) for the downstream voltage samples. In this case, according to a second embodiment, the monitoring method comprises, for each phase:
[0025] - an integration of a first function of the upstream voltage samples on each measurement period to obtain a representative value of the upstream voltage,
[0026] - an integration of a second function of the downstream voltage samples on each measurement period to obtain a representative value of the downstream voltage,
[0027] - a determination of a difference between the representative value of the voltage upstream and the representative value of the downstream voltage, to obtain a first representative value of the voltage across the power relay for each measurement period,
[0028] - an integration of a third function of the current samples on each measurement period, to obtain a second quantity representative of the current flowing in the power relay for each measurement period,
[0029] - a calculation of a ratio between the first and second quantity, or between a average of the first and an average of the second quantities, to obtain the resistance value of the power relay for the measurement period(s).
[0030] Advantageously, the first, second and third functions respectively involve a multiplication of the upstream voltage, downstream voltage and current samples, by respectively a gain of upstream voltage, downstream voltage and current.
[0031] The gains are determined during a calibration phase, at the factory, and make it possible to compensate for the errors introduced by the imprecision of the values of the components used in the sensors.
[0032] The results obtained in the first and second embodiments may, where appropriate, be improved by implementing one or more of the steps listed below:
[0033] - ignore samples associated with a noise-vulnerable current measurement.
[0034] - consider several measurement periods, the average of the first quantities and the the average of the second magnitudes being obtained by applying a selective digital filtering of rectangular impulse response and frequency response of the form sin(x) / x.
[0035] - use a first, a second and a third function which include respectively a Butterworth filtering of said samples, at least of the third order, and having a cutoff frequency for example 3 to 25 times greater than that of the electrical signal.
[0036] According to one variant, when the measurement times of the samples are synchronized with the electrical signal, the integrations are replaced by selections of a maximum value taken over the measurement period in the first and second embodiments of the monitoring method.
[0037] Another aspect of this disclosure relates to a device intended to be mounted between the electrical network and an installation, and which includes a processor assembly configured to implement the monitoring process described above, in its various combinations.
[0038] Another aspect relates to a computer program product comprising instructions which, when executed by at least one processor, cause the implementation of the monitoring process described above.
[0039] Another aspect concerns a non-transient, computer-readable storage medium containing instructions which, when executed by a processor, cause the implementation of the monitoring method described above. Brief description of the figures
[0040] The implementation examples will be better understood in the light of the detailed description that follows and the accompanying drawings, which are given for illustrative purposes only and are not limiting to this disclosure.
[0041] [Fig-1] Fig. 1 is a block diagram of a first example of an electrical device according to this disclosure.
[0042] [Fig.2] The [Fig.2] is a flowchart of a monitoring process intended to be implemented in a device of the type described in the [Fig.1].
[0043] [Fig.3] The [Fig.3] is a block diagram of a second example of an electrical device according to this disclosure.
[0044] [Fig.4] The [Fig.4] is a flowchart of a monitoring process intended to be implemented in a device of the type described in the [Fig.3]. Detailed description
[0045] Various embodiment examples will now be described in more detail, without limitation, with reference to the drawings accompanying this disclosure, which illustrate certain embodiment examples.
[0046] In the following, to simplify the explanation, an electrical device and a monitoring method adapted to the case of a single-phase network are described. This is not limiting. When the network is polyphase, that is to say, when it delivers an electrical signal in several phases, the components and operations described are reproduced for each phase of the network.
[0047] Figure 1 describes an electrical device 10 mounted between a single-phase electrical network 11 and an electrical installation 12. The device 10 includes a current sensor 13, connected in series with a power relay 14. The power relay 14 is connected to the electrical installation and allows the installation 12 to be connected / disconnected from the electrical network 11. The current from the electrical network 11 passes through the sensor 13 and then, when it is closed, through the power relay 14. For example, the current sensor 13 is composed of a resistor (shunt) or a transformer. The current I measured by the current sensor 13 is supplied to an analog-to-digital converter 15. The analog-to-digital converter 15 also receives the voltage V0 measured by a voltage sensor 16 upstream of the current sensor 13, and the voltage VI measured by a voltage sensor 17 downstream of the power relay 14.For example, voltage sensors are made up of resistive dividers.
[0048] The analog-to-digital converter 15 is configured to obtain, at a plurality of measurement times tk (where k is a natural number) over one or more measurement periods, samples V0(k), Vl(k), and I(k) of the upstream voltage, downstream voltage, and current. Typically, the voltage to be measured across the power relay 14 is a few hundred mV, while the voltage at the upstream and downstream points is several hundred volts. For example, a 24-bit sigma-delta converter is used, the resolution of which is sufficient to obtain accurate measurements.
[0049] These samples are provided to a processor assembly 18 of the device 10 which is configured to determine, from the received samples, quantities whose ratio is representative of a resistance value of the power relay, and to generate an alert based on the ratio obtained.
[0050] The alert is transmitted, for example to the electrical network manager 11, via a modem 19 of the device 10.
[0051] In the example of [Fig. 1], the upstream voltage, downstream voltage and current samples are obtained by the same analog-to-digital converter 15. They are therefore synchronous. In this case, advantageously, the processor assembly 18 is configured to execute the process described in [Fig. 2].
[0052] In 21, the upstream voltage samples V0(k), downstream voltage samples Vl(k), and current samples I(k) are supplied by the analog-to-digital converter 15 to the processor assembly 18. In 22, a gain gVo, gVi, and g!, respectively, is applied to the samples V0(k), Vl(k), and I(k). The value of these gains is determined during a calibration phase to compensate for the error introduced by the uncertainty in the sensor components (error in the resistances / in the number of turns of the transformer). The samples obtained are called calibrated samples. In 23, the processor assembly determines, for each measurement instant tk of each measurement period, a difference Ak between the calibrated upstream voltage samples gVo*VO(k) and the calibrated downstream voltage samples gVl*Vl(k). This difference corresponds to the voltage across the contact of power relay 14, because the impedance of the copper arms is very low and therefore negligible compared to the resistance of the contact.For devices where current measurement is performed by a shunt resistor, the potential difference corresponds to the voltage across the contact of the power relay 14 and the shunt resistor.
[0053] In 24, the processor assembly 18 integrates the differences Ak over each measurement period to obtain the RMS value of the voltage difference (Root Mean Square). This RMS value constitutes a first quantity XI representing the voltage across the power relay 14 for each measurement period. In 25, it integrates the calibrated current samples I(k) over each measurement period to obtain an RMS value of the current. The RMS value of the current constitutes a second quantity X2 representing the current flowing through the power relay for each measurement period. In 26, the processor assembly calculates the ratio between the first and second quantities, or between an average of the first and an average of the second quantities, to obtain the resistance value of the power relay for the measurement period(s).
[0054] The integration time can vary. For example, the resistance value of the power relay can be determined for each period of the electrical signal (i.e., for a 50 Hz electrical signal, every 20 ms). It is also possible to integrate over longer periods to obtain more averaged and therefore more precise values. Advantageously, integration is performed over one or more complete periods of the electrical signal.
[0055] Figure 3 describes another variant of an electrical device mounted between a single-phase electrical network 11 and an electrical installation 12. The device 30 differs from the device 10 in that it comprises two analog-to-digital converters 35 and 36. The current I measured by the current sensor 13 is supplied to the first analog-to-digital converter 35. The analog-to-digital converter 35 also receives the voltage V0 measured by a voltage sensor 16 upstream of the current sensor. 13. It provides the processor assembly 18 with the samples V0(k) and I(k). The second analog-to-digital converter 36 receives the voltage V1 measured by a voltage sensor 17 downstream of the power relay 14. It provides the processor assembly 18 with the samples Vl(k).
[0056] In the example in [Fig. 3], the upstream voltage, downstream voltage, and current samples are obtained by two different analog-to-digital converters and are therefore not synchronous. In this case, advantageously, the processor assembly 18 is configured to execute the process described in [Fig. 4]. This configuration is found, for example, in older electricity meters already installed in the network. The software version of these meters can be updated to implement the algorithm described with reference to [Fig. 4].
[0057] In 41, the upstream voltage samples V0(k) and current samples I(k) are supplied by the analog-to-digital converter 35 to the processor assembly 18. The downstream voltage samples Vl(k) are supplied by the analog-to-digital converter 36 to the processor assembly 18. In 42, a gain gVo, gVl, and gl, respectively, is applied to the samples V0(k), Vl(k), and I(k). The value of these gains is determined during a calibration phase to compensate for the error introduced by the uncertainty in the sensor components. The resulting samples are called calibrated samples. In 43, the integrated processor assembly, the calibrated upstream voltage samples gV0*V0(k) over the measurement period to obtain an effective value of the upstream voltage denoted RMS0, and the calibrated downstream voltage samples gVl*V 1 (k) over the measurement period to obtain an effective value of the downstream voltage, denoted RMSi.In step 44, the difference between the upstream RMS voltage and the downstream RMS voltage is calculated. This difference constitutes a first quantity XI representing the voltage across the power relay for each measurement period. In step 45, the processor integrates the calibrated current samples I(k) over each measurement period to obtain an RMS current value. The RMS current value constitutes a second quantity X2 representing the current flowing through the power relay for each measurement period. In step 46, the processor calculates the ratio between the first and second quantities, or between an average of the first and second quantities, to obtain the resistance value R of the power relay for the measurement period(s).
[0058] Advantageously, samples corresponding to a low current measurement are ignored because they are vulnerable to noise. For example, if the measured current is below a threshold, the associated measurements are not taken into account in the calculations. Typically, measurements are usable above a current of 10 A.
[0059] In the example of Figures 2 and 4, the first, second, and third functions applied at 22 and 42 to the upstream and downstream voltage and current samples are multiplicative functions that multiply the samples by predetermined calibration gains. In one embodiment, in addition to applying a calibration gain, these functions include Butterworth filtering of the calibrated samples, at least of the third order, and having a cutoff frequency 3 to 25 times higher than that of the signal.
[0060] When the measurement times of the samples are synchronized with the electrical signal, the integration operation can be replaced by selecting the sample with the maximum value over the measurement period. For example, the maximum values obtained can then be averaged over several measurement periods. This can be achieved by a selective digital filter with a rectangular impulse response and a frequency response of the form sin(x) / x.
[0061] It should be noted that the second converter 36 can be integrated into the processor assembly 18. Integrated converters are generally less precise (typically 12 bits instead of 24 bits for converters 15 or 35). A resolution of 12 bits is generally sufficient for measuring the voltage at the downstream point.
[0062] It is also possible to use the embodiment of [Fig.4] with a device according to [Fig.1] (a single converter 15). However, the results are less precise.
[0063] Those skilled in the art will understand that all the functional diagrams presented here represent conceptual views, given by way of example, of circuits incorporating the disclosure principles. The specific structural and functional details described herein are non-limiting examples. The disclosure can be realized in many different forms and should not be interpreted as being limited to the realizations presented herein as illustrative examples.
Claims
Demands
1. An electrical device intended to be mounted between the electrical network and an electrical installation, the electrical network delivering an electrical signal in one or more phases, the device comprising at least: - for each phase, a current sensor mounted in series with a power relay and intended to measure a current flowing in the power relay when it is closed, the current sensor being intended to be connected to the electrical network at an upstream point and the power relay being intended to be connected to the installation at a downstream point, - for each phase, a first voltage sensor mounted at the upstream point to measure an upstream voltage, - for each phase, a second voltage sensor mounted at the downstream point to measure a downstream voltage, - at least one analog-to-digital converter, configured to obtain, for each phase, at a plurality of measurement times over one or more measurement periods, samples of the upstream voltage,of the downstream voltage and current, - a processor-based assembly configured to determine, for each phase, from the samples obtained, quantities whose ratio is representative of a resistance value of the power relay, and to generate an alert based on the ratio obtained, and - a modem to transmit the alert.
2. An electrical device according to claim 1, characterized in that the upstream voltage, downstream voltage, and current samples are obtained from the same analog-to-digital converter, and the processor assembly is configured to, for each phase: - determine, for each measurement instant of each measurement period, a difference between a first function of the upstream voltage samples and a second function of the downstream voltage samples, - integrate the differences determined over each measurement period to obtain a first quantity representing the voltage across the power relay for each measurement period, - integrate a third function of the current samples over each measurement period to obtain a second quantity representative of the current flowing in the power relay for each measurement period, - calculate the ratio between the first and second quantity, or between an average of the first and an average of the second quantities, to obtain the resistance value of the power relay for the measurement period(s).
3. An electrical device according to claim 1, characterized in that the samples are obtained from a plurality of analog-to-digital converters and the processor assembly is configured to, for each phase: - integrate a first function of the upstream voltage samples over each measurement period to obtain a representative value of the upstream voltage, - integrate a second function of the downstream voltage samples over each measurement period to obtain a representative value of the downstream voltage, - determine a difference between the representative value of the upstream voltage and the representative value of the downstream voltage, to obtain a first quantity representative of a voltage across the power relay for each measurement period, - integrate a third function of the current samples over each measurement period,To obtain a second quantity representing the current flowing through the power relay for each measurement period, calculate the ratio between the first and second quantities, or between an average of the first and an average of the second quantities, to obtain the resistance value of the power relay for the measurement period(s).
4. Device according to any one of claims 1 to 3, characterized in that the first, second and third functions respectively comprise a multiplication of the upstream voltage, downstream voltage and current samples, by respectively a gain of upstream voltage, downstream voltage and current.
5. Electrical device according to any one of claims 2 to 4, characterized in that the average of the first quantities and the average of the second quantities are obtained by applying a digital selective filtering of rectangular impulse response and frequency response of the form sin(x) / x.
6. Device according to any one of claims 2 to 5, characterized in that the first, second and third functions respectively comprise a Butterworth filtering of said samples, at least of the third order, and having a cutoff frequency 3 to 25 times greater than that of the signal.
7. Device according to any one of claims 1 to 6, characterized in that a measurement period comprises one or more whole periods of the signal.
8. Device according to any one of claims 1 to 7, characterized in that when the measurement times of the samples are synchronized with the electrical signal, the processor assembly is configured to, instead of integrating, select a maximum value taken over the measurement period.
9. Device according to any one of claims 1 to 8, characterized in that the processor assembly is configured to ignore samples associated with a noise-vulnerable current measurement.
10. A method for monitoring an electrical device intended to be mounted between the electrical network and an installation, the electrical network delivering an electrical signal to one or more phases, the device comprising at least: - for each phase, a current sensor mounted in series with a power relay and intended to measure a current flowing in the power relay when it is closed, the current sensor being intended to be connected to the electrical network at an upstream point and the power relay being intended to be connected to the installation at a downstream point, - for each phase, a first voltage sensor mounted at the upstream point to measure an upstream voltage, - for each phase, a second voltage sensor mounted at the downstream point to measure a downstream voltage, - at least one analog-to-digital converter, configured to obtain, for each phase, at a plurality of measurement times over one or more measurement periods,samples of upstream voltage, downstream voltage and current, - a transmission modem, the monitoring method comprising: - a determination for each phase, from the samples obtained, of quantities whose ratio is representative of a resistance value of the power relay for the measurement period, - a generation of alert based on the ratio obtained, and - a transmission of alert via the transmission modem.
11. A monitoring method according to claim 10, characterized in that the upstream voltage, downstream voltage and current samples are obtained from the same analog-to-digital converter, and the method comprises: - a determination, for each measurement instant of each measurement period, of a difference between a first function of the upstream voltage samples and a second function of the downstream voltage samples, - an integration of the differences determined over each measurement period, to obtain a first representative value of the voltage across the power relay for each measurement period, - an integration of a third function of the current samples over each measurement period, to obtain a second quantity representative of the current flowing in the power relay for each measurement period, - a calculation of a ratio between the first and second quantity, or between an average of the first and an average of the second quantities, to obtain the resistance value of the power relay for the measurement period(s).
12. A monitoring method according to claim 10, characterized in that the samples are obtained from a plurality of analog-to-digital converters and the method comprises, for each phase: - an integration of a first function of the upstream voltage samples over each measurement period to obtain a representative value of the upstream voltage, - an integration of a second function of the downstream voltage samples over each measurement period to obtain a representative value of the downstream voltage, - a determination of the difference between the representative value of the upstream voltage and the representative value of the downstream voltage, to obtain a first quantity representative of a voltage across the terminals of the power relay for each measurement period, - an integration of a third function of the current samples over each measurement period, to obtain a second quantity representative of the current flowing in the power relay for each measurement period, - a calculation of a ratio between the first and second quantities, or between an average of the first and an average of the second quantities, to obtain the resistance value of the power relay for the measurement period(s).
13. A monitoring method according to any one of claims 11 or 12, characterized in that the first, second and third functions respectively comprise a multiplication of the upstream voltage, downstream voltage and current samples, by respectively a gain of upstream voltage, downstream voltage and current.
14. A monitoring method according to any one of claims 10 to 13, characterized in that the average of the first quantities and the average of the second quantities are obtained by applying a selective digital filtering of rectangular impulse response and frequency response of the form sin(x) / x.
15. A monitoring method according to any one of claims 11 to 14, characterized in that the first, second and third functions respectively comprise a Butterworth filtering of said samples, at least of the third order, and having a cutoff frequency 3 to 25 times greater than that of the signal.
16. A monitoring method according to any one of claims 10 to 15, characterized in that when the measurement times of the samples are synchronized with the electrical signal, the integrations are replaced by selections of a maximum value taken over the measurement period.
17. A monitoring method according to any one of claims 10 to 16, characterized in that it ignores samples having an amplitude that makes them vulnerable to noise.
18. Product computer program comprising instructions which, when executed by at least one processor, cause the implementation of a process according to any one of claims 10 to 17.
19. Computer-readable non-transient storage medium comprising instructions which, when executed by a processor, cause the implementation of a method according to any one of claims 10 to 18.