Serial clock synchronization

Abstract

Method for synchronizing a clock (9) of an electric meter (1) which comprises a first processing unit (5) comprising a first port (8) arranged to be connected to an external device (2), comprising the steps of: receiving via the first port (8) a first frame containing a reference time; configuring the first port to operate in an interrupt trigger mode; receiving via the first port a pulse defining a synchronization time, and triggering an interrupt leading to recording the reference time as being a current time at the synchronization time; reconfiguring the first port to communicate via the first port using the serial link. FIGURE OF THE ABSTRACT: Fig.1

Description

Title of the invention: Clock synchronization by serial link

[0001] The invention relates to the field of electrical meters, and in particular industrial meters.

[0002] BACKGROUND OF THE INVENTION

[0003] Some modern industrial electricity meters are designed to measure, in addition to the electrical energy consumption of the installation to which they are connected, quality parameters of the power supply supplied by the electrical energy distribution network.

[0004] Power quality parameters include, but are not limited to, the frequency and amplitude of the supply voltage, dips, overvoltages, voltage interruptions, voltage imbalance, etc.

[0005] The International Electrotechnical Commission (IEC) has produced the quality standard IEC 61000-4-30 which defines how to measure these parameters.

[0006] To comply with the IEC 61000-4-30 class A standard, electricity meters must have a very precise clock which allows them to very precisely time-stamp the occurrence of different events on the network.

[0007] The very precise time stamping of events makes it possible, in particular, by analyzing the data from several meters, to know where in the network the event occurred.

[0008] This clock must not drift by more than one network period from UTC time (for Coordinated Universal Time), which corresponds, for a supply voltage frequency of 60 Hz, to + / - 16.67 ms.

[0009] However, the internal clocks of the counters have a natural drift linked mainly to the oscillators. It is therefore advisable to regularly resynchronize the counters to UTC time.

[0010] In order to achieve time synchronization, some current meters are equipped with a hardware signal (All or Nothing input) often called "TOP SYNCHRO signal", allowing a reference clock (having access to UTC time) to synchronize the internal clock of the meter. This solution therefore requires a dedicated port, which increases the cost of the meter.

[0011] Other meters include an NTP server (for Network Time Protocol) allowing this synchronization, either through a radio link (GPS), or via a wired link with the IEEE 1588 protocol (Ethernet link).

[0012] These solutions tend to no longer be accepted by energy distributors or even by subscribers, because they are easily “hackable”. These solutions are also relatively expensive.

[0013] SUBJECT OF THE INVENTION

[0014] The object of the invention is to resynchronize the internal clock of an electric meter, in a simple, inexpensive and secure manner. Summary of the invention

[0015] With a view to achieving this aim, a method is proposed for synchronizing an internal clock of an electric meter which comprises a first processing unit comprising a first port arranged to be connected to external equipment, the synchronization method comprising the first steps, implemented successively by the first processing unit and repeated at predefined intervals, of: • receive via the first port a first frame sent by the external equipment using a serial link, and containing a reference time; • configure the first port to operate in an interrupt trigger mode; • receive via the first port a pulse, emitted by the external equipment and defining a synchronization time, and trigger an interrupt leading to recording the reference time as being a current time at the synchronization time; • reconfigure the first port to communicate via the first port using the serial link.

[0016] The synchronization of the internal clock of the electric meter is therefore carried out by equipment external to the meter, a modem for example, via the serial link. It is therefore possible to use a pre-existing serial link, so that the implementation of the synchronization method does not require an additional connection and is simple and inexpensive to carry out. This serial link is difficult to hack.

[0017] A synchronization method is further proposed as previously described, in which the first steps further comprise the step, following reception of the first frame, of transmitting via the first port, to the external equipment and using the serial link, a second frame containing an acknowledgment message.

[0018] A synchronization method is further proposed as previously described, in which a duration between the transmission of the first frame and the transmission of the second frame is a predefined duration of between 1 s and 3 s.

[0019] We further propose a synchronization method as previously described, in which the first steps further comprise the step, following the reconfiguration of the first port, of transmitting via the first port, to the external equipment and in using the serial link, a third frame containing information on the end of time setting.

[0020] We further propose a synchronization method as previously described, in which the interrupt is a rising edge interrupt.

[0021] A synchronization method is further proposed as previously described, in which the serial link is an RS-232 link.

[0022] We further propose an electric meter comprising a first processing unit comprising a first port, in which the first steps of the synchronization method as previously described are implemented.

[0023] An electric meter as previously described is further provided, the electric meter being further arranged to monitor an electrical energy distribution network to which it is connected, to time-stamp events occurring on the electrical energy distribution network using the current time, and to transmit network monitoring information to the external equipment using the serial link.

[0024] A computer program is further provided comprising instructions which cause the first processing unit of the electric meter as previously described to execute the first steps of the synchronization method as previously described.

[0025] A computer-readable recording medium is further provided, on which the computer program as previously described is recorded.

[0026] A method is further proposed for synchronizing an internal clock of an electric meter arranged to be connected to external equipment which comprises a second processing unit comprising a second port arranged to be connected to the electric meter, the synchronization method comprising the second steps, implemented successively by the second processing unit and repeated at predefined intervals, of: • transmit via the second port, to the electricity meter and using a serial link, a first frame containing a reference time; • configure the second port to operate in a pulse generation mode; • transmit via the second port, to the electricity meter, a pulse defining a synchronization time; • reconfigure the second port to communicate via the second port using the serial link.

[0027] A synchronization method is further proposed as previously described, in which the pulse has a duration defined with an accuracy of + / - 1 ms.

[0028] A synchronization method is further proposed as previously described, in which the second steps further comprise the step, following the transmission of the first frame, of waiting, before configuring the second port so that it operates in the pulse generation mode, to receive via the second port a second frame containing an acknowledgment message.

[0029] A modem is further proposed comprising a second processing unit comprising a second port, in which the second steps of the synchronization method as previously described are implemented.

[0030] A computer program is further provided comprising instructions which cause the second processing unit of the modem as previously described to execute the second steps of the synchronization method as previously described.

[0031] A computer-readable recording medium is further provided, on which the computer program as previously described is recorded.

[0032] A system is further proposed comprising an electric meter as previously described, and a modem as previously described.

[0033] The invention will be better understood in light of the following description of a particular non-limiting embodiment of the invention. Brief description of the drawings

[0034] Reference will be made to the attached drawings, among which:

[0035] [Fig-1] [Fig. 1] represents a system comprising an electric meter and a modem;

[0036] [Fig.2] [Fig.2] illustrates a synchronization phase of the counter clock;

[0037] [Fig.3] [Fig.3] represents the steps of a synchronization phase. DETAILED DESCRIPTION OF THE INVENTION

[0038] With reference to [Fig.l], the system 0 comprises a meter 1 and equipment external to the meter 1, in this case a modem 2.

[0039] The meter 1 is an industrial electric meter which is here connected to an electric energy distribution network 3 which is a three-phase network and which comprises a first phase L1, a second phase L2, a third phase L3 and a neutral N.

[0040] The electric meter 1 is connected to an industrial electrical installation, to which the network 3 supplies electrical energy.

[0041] Meter 1 is also connected to modem 2.

[0042] The counter 1 comprises a first processing unit 5.

[0043] The first processing unit 5 is here designed, conventionally, to acquire and process current and voltage measurements made by the sensors of the meter 1, so as to measure the electrical energy consumed by the installation.

[0044] The first processing unit 5 is also designed to measure quality parameters of the power supply supplied by the network 3, and to time-stamp events occurring on the network 3.

[0045] The first processing unit 5 comprises at least one first processing component 6.

[0046] The first processing component 6 is for example a “generalist” processor, a microcontroller, a processor specialized in signal processing (or DSP, for Digital Signal Processor), or a programmable logic circuit such as an FPGA (for Field Programmable Gate Arrays) or an ASIC (for Application Specific Integrated Circuit).

[0047] The first processing component 6 is here a microcontroller.

[0048] The first processing unit 5 further comprises one or more memories 7, connected to or integrated in the first processing component 6. At least one of these memories 7 forms a computer-readable recording medium, on which is recorded at least one computer program comprising instructions which cause the first processing component 6 to execute the first steps of the synchronization phases which will be described.

[0049] The first processing unit 5 comprises at least one first port 8, which can be configured according to a serial communication mode, in which the first port 8 can be used to implement a serial link (here RS-232), and in an interrupt triggering mode.

[0050] The first port 8 is a port of the first processing component 6 and comprises two pins of the first processing component 6.

[0051] The first port 8 is here a port configurable in UART mode (for Universal Asyn-chronous Receiver Transmitter) or in GPIO mode (for General Purpose Input / Output).

[0052] Thus, here, the serial communication mode corresponds to the UART mode, and the interrupt trigger mode corresponds to the GPIO mode.

[0053] The first processing unit 5 also comprises an internal clock 9, which is used in particular to time-stamp the events mentioned earlier occurring on the distribution network 3.

[0054] The modem 2 is designed to form a communication interface between the meter 1 (and possibly other meters) and a communication network 10 (the Internet network for example). The meter 1 therefore communicates with the network 10 via the modem 2.

[0055] Modem 2 has access to UTC time through its connection with network 10.

[0056] The modem 2 comprises a second processing unit 11 comprising at least one second processing component 12.

[0057] The second processing component 12 is for example a “generalist” processor, a microcontroller, a processor specialized in signal processing (or DSP, for Digital Signal Processor), or a programmable logic circuit such as an FPGA (for Field Programmable Gate Arrays) or an ASIC (for Application Specific Integrated Circuit).

[0058] The second processing component 12 is here a microcontroller.

[0059] The second processing unit 11 further comprises one or more memories 14, connected to or integrated into the second processing component 12. At least one of these memories 14 forms a computer-readable recording medium, on which is recorded at least one computer program comprising instructions which cause the second processing component 12 to execute the second steps of the synchronization phases which will be described.

[0060] The second processing unit 11 comprises at least one second port 15, which can be configured according to a serial communication mode, in which the second port 15 can be used to implement the serial link (here RS-232), and a pulse generation mode, allowing interrupts to be generated in the first processing unit 5 from outside the counter 1.

[0061] The second port 15 is a port of the second processing component 12 and comprises two pins of the second processing component 12.

[0062] The second port 15 is a port configurable in UART mode or in GPIO mode.

[0063] Thus, here, the serial communication mode corresponds to the UART mode, and the mode pulse generation corresponds to GPIO mode.

[0064] The first port 8 of the meter 1 and the second port 15 of the modem 2 are connected by a cable 16 comprising two wires 17, 18 each connecting a pin of the first port 8 to a pin of the second port 15.

[0065] When the first port 8 and the second port 15 are configured in the serial communication mode, the meter 1 and the modem 2 exchange data using the RS-232 serial link, via the first port 8, the second port 15 and the wires 17, 18. The modem 2 transmits data to the meter 1 via the wire 17, and the meter 1 transmits data to the modem 2 via the wire 18.

[0066] Regularly, with reference to figures 2 and 3, the modem 2 triggers the synchronization of the internal clock 9 of the counter 1 to UTC time.

[0067] The synchronization phase is repeated at predefined intervals (fixed or variable), for example every day or every week.

[0068] Each synchronization phase comprises first steps E1, implemented successively by the first processing unit 5 of the electricity meter 1, and second steps E2, implemented successively by the second processing unit 11 of the modem 2.

[0069] The first steps E1 and the second steps E2 are therefore repeated at predefined intervals.

[0070] Each synchronization phase begins while the first port 8 and the second port 15 are in serial communication mode.

[0071] The modem 2 acquires the UTC time on the network 10 and produces from the UTC time a reference time corresponding to the current time at a synchronization time Tsync.

[0072] Then, at a predefined time preceding the time Tsync, for example at Tsync - 3 s, the second processing unit 11 of the modem 2 transmits via the second port 15, to the counter 1 and using the serial link, a first frame 21 containing the reference time: step E2a.

[0073] The reference time is for example expressed in hours, minutes, seconds, and milliseconds, and for example in the format:

[0074] hh.mm.ss.ms

[0075] with h for hour, m for minute, s for second, ms for millisecond.

[0076] The first processing unit 5 of the counter 1 then receives the first frame 21 via the first port 8.

[0077] Following reception of the first frame 21, the counter 1 transmits via the first port 8, to the modem 2 and using the serial link, a second frame 22 containing an acknowledgment message: step El a.

[0078] The duration between the transmission of the first frame 21 and the transmission of the second frame 22 is equal to a predefined duration, which is for example between 1 s and 3 s.

[0079] Here, this predefined duration is less than a maximum duration of, for example, 2s.

[0080] The second frame 22 is transmitted at a time preceding Tsync with a duration of, for example, 1 s.

[0081] This “timeout” of 2 s (for example) is added so as not to block RS-232 communication.

[0082] As long as this acknowledgment frame 22 is not transmitted, the modem 2 retransmits the first frame 21 containing the reference time.

[0083] After having transmitted the second frame 22, the first processing unit 5 of the counter 1 configures the first port 8 to operate in interrupt mode: step Elb.

[0084] The second processing unit 11 of the modem 2 configures the second port 15 to operate in the pulse generation mode: step E2b.

[0085] The second processing unit 11 then transmits via the second port 15, to the counter 1, a pulse 23: step E2c.

[0086] This pulse 23 begins with a falling edge and ends with a rising edge. The pulse is calibrated very precisely. It has a defined duration with a accuracy of + / - 1 ms. This duration is 10 ms here.

[0087] Pulse 23 defines the synchronization time, which here corresponds to the rising edge. Pulse 23 is therefore emitted at time:

[0088] Tsync - 10 ms.

[0089] The first processing unit 5 then receives this pulse 23 via the first port 8, and triggers an interrupt leading to recording the reference time as being the current time at the synchronization time: step Elc.

[0090] The interrupt here is a rising edge interrupt.

[0091] The first processing unit 5 reconfigures the first port 8 to communicate via the first port 8 using the serial link (serial communication mode). The modem 2 reconfigures the second port 15 to communicate via the second port 15 using the serial link (serial communication mode).

[0092] The first processing unit 5 then transmits via the first port 8, to the modem 2 and using the serial link, a third frame 24 containing information on the end of time setting: step Eld.

[0093] Synchronization is complete.

[0094] Clock 9 of counter 1 is resynchronized. The current time is extremely precise. Its accuracy depends mainly on the accuracy of the definition of time Tsync and therefore on the accuracy of the duration of pulse 23 which, as we have seen, has been calibrated very precisely.

[0095] The meter 1 thus monitors the electrical energy distribution network 3 to which it is connected, and, in particular, very precisely timestamps events occurring on the distribution network 3 using the current time. The meter 1 produces, from this monitoring, monitoring information for the network 3 (including the time-stamped events), and transmits the monitoring information for the network 3 to the modem 2 via the cable 16 using the serial link.

[0096] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0097] The serial link is not necessarily an RS-232 link, it could be another type of serial link, for example RS-485.

[0098] The synchronization time is defined by the interrupt (and therefore the pulse), but it could be a time other than that of a rising edge (and for example that of a falling edge, or a time defined by a predetermined duration following the interrupt).

[0099] The durations cited here (2 s, 10 ms, etc.) could be different.

[0100] The equipment connected to the meter is not necessarily a modem, it can be any equipment that can be connected to a meter by a serial link and having access to UTC time (e.g. a data concentrator).

[0101] The step of transmitting the second frame is not mandatory: the modem could transmit the pulse generating the interrupt without waiting for acknowledgment. Similarly, the step of transmitting the third frame is not mandatory.

[0102] The invention can be implemented with a single-phase or polyphase meter (regardless of the number of phases).

Claims

Claims

1. Method for synchronizing an internal clock (9) of an electric meter (1) which comprises a first processing unit (5) comprising a first port (8) arranged to be connected to an external equipment (2), the synchronization method comprising the first steps (El), implemented successively by the first processing unit (5) and repeated at predefined intervals, of: • receiving via the first port (8) a first frame (21) transmitted by the external equipment using a serial link, and containing a reference time; • configuring the first port so that it operates in an interrupt trigger mode; • receiving via the first port a pulse (23), transmitted by the external equipment and defining a synchronization time, and triggering an interrupt leading to recording the reference time as being a current time at the synchronization time;• reconfigure the first port to communicate via the first port using the serial link.;

2. Synchronization method according to claim 1, in which the first steps further comprise the step, following reception of the first frame (21), of transmitting via the first port (8), to the external equipment and using the serial link, a second frame (22) containing an acknowledgment message.

3. A synchronization method according to claim 2, wherein a duration between the transmission of the first frame (21) and the transmission of the second frame (22) is a predefined duration of between 1 s and 3 s.

4. Synchronization method according to one of the preceding claims, in which the first steps further comprise the step, following the reconfiguration of the first port (8), of transmitting via the first port (8), to the external equipment (2) and using the serial link, a third frame (24) containing information on the end of time setting.

5. Synchronization method according to one of the preceding claims, in which the interrupt is a rising edge interrupt.

6. Synchronization method according to one of the preceding claims, in which the serial link is an RS-232 link.

7. Electricity meter (1) comprising a first processing unit (5) comprising a first port (8), in which the first steps of the synchronization method according to one of the preceding claims are implemented.

8. An electric meter (1) according to claim 7, the electric meter being further arranged to monitor an electric power distribution network (3) to which it is connected, to time-stamp events occurring on the electric power distribution network using the current time, and to transmit network monitoring information to the external equipment (2) using the serial link.

9. Computer program comprising instructions which cause the first processing unit (5) of the electricity meter (1) according to one of claims 7 or 8 to execute the first steps of the synchronization method according to one of claims 1 to 6.

10. A computer-readable recording medium on which the computer program according to claim 9 is recorded.

11. Method for synchronizing an internal clock (9) of an electric meter (1) arranged to be connected to external equipment (2) which comprises a second processing unit (11) comprising a second port (15) arranged to be connected to the electric meter, the synchronization method comprising the second steps (E2), implemented successively by the second processing unit (11) and repeated at predefined intervals, of: • transmitting via the second port (15), to the electric meter and using a serial link, a first frame (21) containing a reference time; • configuring the second port (15) so that it operates in a pulse generation mode; • transmitting via the second port (15), to the electric meter, a pulse (23) defining a synchronization time; • reconfiguring the second port to communicate via the second port using the serial link.

12. A synchronization method according to claim 11, wherein the pulse (23) has a duration defined with an accuracy of + / - 1 ms.

13. Synchronization method according to one of claims 11 or 12, wherein the second steps further comprise the step, following the transmission of the first frame (21), of waiting, before configuring the second port (15) to operate in the pulse generation mode, to receive via the second port (15) a second frame (22) containing an acknowledgment message.

14. Modem (2) comprising a second processing unit (11) comprising a second port (15), in which the second steps of the synchronization method according to one of claims 11 to 13 are implemented.

15. Computer program comprising instructions which cause the second processing unit (11) of the modem (2) according to claim 14 to execute the second steps of the synchronization method according to one of claims 11 to 13.

16. A computer-readable recording medium on which the computer program according to claim 15 is recorded.

17. System (0) comprising an electric meter (1) according to one of claims 7 or 8, and a modem (2) according to claim 14.

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