Method and system for calibrating voltage measurements in an electrical quantity measurement system

Abstract

Procedure and system for calibrating voltage measurements in an electrical quantity measurement system. This calibration system (2) includes a calibration device (10) configured to determine a first reference time instant of a zero-crossing event of the voltage signal it measures, and to transmit a calibration message including said first reference time instant and a measured voltage amplitude value to at least one electrical quantity measurement device (4), configured to receive said calibration message, extract said first reference time instant and the voltage amplitude, determine a second reference time instant, of zero crossing of the locally measured voltage signal, corresponding to said first reference instant, calculate a phase shift of the locally measured voltage signal,based on the difference between the first and second reference time instants, apply a voltage calibration in phase and amplitude as a function of the voltage amplitude and phase shift. Figure for the abbreviation: Figure 1,

Description

Description Title of the invention: Method and system for calibrating voltage measurements in a system for measuring electrical quantities

[0001] — The present invention relates to a method and a system for calibrating measurements of voltage in an electrical quantity measurement system.

[0002] = The invention lies in the field of measurement and calculation of quantities electrical, in a distributed manner, in an electrical installation.

[0003] — Indeed, in electrical installations, for example local distribution networks, electricity supply, it is useful to measure electrical quantities, in particular the electric current, voltage, on various electrical conductors, in several lo- network measurements, and to calculate other electrical quantities, eg power, energy etc.

[0004] — For example, devices are known for measuring electrical quantities, eg current or voltage sensors, which have communication interfaces, for example example for the communication of measured electrical quantities, which allows implement a communication network between measuring devices to a gateway communication device, which facilitates the supervision and control of the power grid by users.

[0005] — In addition, a calculation of other electrical quantities from the current and voltage measured by such sensors can be advantageously achieved in such a communication network.

[0006] In particular, the invention applies in the case of a distributed system for measuring electrical quantities comprising a plurality of quantity measuring devices electrical devices equipped with voltage measurement modules by capacitive coupling. In such a system, voltage measurement by capacitive coupling, without direct connection to the electrical conductor concerned, is likely to introduce a time delay. However, the alternating electrical signals circulating in an electrical installation are each ca- characterized by an amplitude and a phase. A time delay results in a shift phase or phase shift in voltage measurements. In a distributed system of measurement of electrical quantities, the electrical quantities being calculated for alternating current and voltage signals, it is important to synchronize tempo- actually the various measurements in order to obtain calculations of electrical quantities, such as power, good precision. For this purpose, it is important to calibrate the measurements obtained by the various quantity measuring devices electrical located in various places of the electrical installation, the calibration concerning the amplitude and / or phase of the measured electrical signals. The invention aims to propose a solution for calibrating voltage measurements in such a distributed system for measuring electrical quantities. To this end, the invention proposes, according to one aspect, a system for calibrating voltage measurements in a system for measuring electrical quantities by a plurality of electrical quantity measuring devices distributed in an electrical installation, each device for measuring electrical quantities comprising - a voltage measurement module by capacitive coupling, - a communication interface configured to communicate according to a communication protocol, - a local clock allowing dating of events in a local time frame, the system further comprising a single calibration device, configured to measure a voltage signal by contact with one or each electrical conductor of the electrical installation, the calibration device comprising a communication interface configured to communicate according to said communication protocol and a local clock. This system further comprises a synchronization device comprising a so-called synchronization clock, allowing event dating in a reference time frame, said devices for measuring electrical quantities and the calibration device each being configured to communicate with the synchronization device and to implement a mechanism for synchronizing the local clock with the synchronization clock, allowing event dating in said reference time frame. The calibration device is configured to: determine a first reference time instant, in the reference time frame, of a zero crossing event of said voltage signal measured by the calibration device, transmit a calibration message comprising said first reference time instant and a measured voltage amplitude value to at least one device measuring electrical quantities and, said at least one electrical quantity measuring device is configured to: receiving said calibration message from the calibration device, and extracting said first reference time instant and the voltage amplitude, determine a second time instant of zero crossing of the voltage signal measured locally, in the reference time frame, called the second reference time instant, corresponding to said first reference instant, calculate a phase shift of the locally measured voltage signal, as a function of the difference between the first reference time instant and the second reference time instant, apply a voltage calibration in phase and amplitude based on the received voltage amplitude and the calculated phase shift. Advantageously, the proposed calibration system allows a phase shift calculation for each electrical quantity measuring device. The distributed voltage measurement calibration system according to the invention may have one or more of the following characteristics, taken independently or in any acceptable combination. The electrical quantity measuring device is configured to store a plurality of second time instants, expressed in the reference frame, of zero crossing of the locally measured voltage signal. For the determination of the second reference time instant, said electrical quantity measuring device is configured to determine among the second stored time instants, the second zero crossing time instant closest to said first reference time instant. The calibration device is configured to broadcast said calibration message to all electrical quantity measuring devices. The communication protocol is the ZigBee Green Power protocol. The synchronization device is configured to successively send synchronization messages to at least one communicating device among the electrical quantity measuring devices and said calibration device, the successive synchronization messages comprising at least one current synchronization message and a previous synchronization message, the current synchronization message containing an incremental synchronization message identifier and a time instant of sending the previous synchronization message, each communicating device receiving said synchronization messages being configured to store a local synchronization table, storing information relating to time instants, in the local time frame, of reception of messages from the synchronization device and the time instants of sending said synchronization messages, in the reference time frame,by the synchronization device. , Each communicating device is configured to calculate a correspondence between the local clock of said communicating device and the reference clock using the local synchronization table. The synchronization device is a gateway communication device, comprising a communication interface configured to communicate according to said communication protocol. According to another aspect, the invention relates to a method for calibrating voltage measurements implemented in a calibration system as described above, comprising steps: -by the calibration device: - determine a first reference time instant, in the reference time frame, of a zero crossing event of said voltage signal measured by the calibration device, -Transmit a calibration message comprising said first reference time instant and a measured voltage amplitude value to at least one device measuring electrical quantities, - by at least one device for measuring electrical quantities: receiving said calibration message from the calibration device, and extracting said first reference time instant and the voltage amplitude, determine a second time instant of zero crossing of the voltage signal measured locally, in the reference time frame, called the second reference time instant, corresponding to said first reference instant, calculate a phase shift of the locally measured voltage signal, as a function of the difference between the first reference time instant and the second reference time instant, apply a voltage calibration in phase and amplitude based on the received voltage amplitude and the calculated phase shift. This process has the same advantages as the calibration system. The method for calibrating distributed voltage measurements according to the invention may have one or more of the characteristics below, taken independently or in all acceptable combinations. The synchronization mechanism comprises, by the synchronization device, sending successive synchronization messages to at least one communicating device among the electrical quantity measurement devices and the calibration device, the successive messages comprising at least one current synchronization message and one previous synchronization message, the current synchronization message comprising an incremental synchronization message identifier and a time instant of sending of the previous message. The calibration and synchronization messages are sent by said synchronization device, grouped into calibration and synchronization messages, to said electrical quantity measuring devices. Other characteristics and advantages of the invention will emerge from the description given below, for information purposes only and in no way limiting, with reference to the appended figures, among which: [Fig.1] [Fig.1] schematically represents a distributed system for measuring electrical quantities in an electrical installation; [Fig.2] [Fig.2] is a graph illustrating two representative curves of voltage signals and the phase shift between these two curves; [Fig.3] [Fig.3] schematically represents a synchronization method between a communicating device and the synchronization device in one embodiment: [Fig.4] [Fig.4] represents the main steps of a calibration process according to one embodiment. The invention applies in particular to a system for measuring electrical quantities in an electrical installation as described in [Fig.1]. It should be noted that the invention applies more generally to the calibration of voltage measurements in an electrical installation, provided by a plurality of measuring devices equipped with voltage measurement modules by capacitive coupling, inducing a measurement delay which results in a phase shift. [Fig.1] schematically illustrates a system for measuring electrical quantities 2, the measurements being carried out in a distributed manner, in an electrical installation. The electrical installation, which is not shown in [Fig. 1], is for example a domestic electricity distribution installation or an electricity distribution installation for a commercial, industrial or tertiary building, configured to supply electrical energy and electrical energy consuming loads (not shown), connected by means of electrical conductors 8, from one or more sources of electrical energy, including in particular a public electricity distribution network supplying an alternating current, and, optionally, local sources e.g. photovoltaic panels. The electrical conductors 8 are, for example, cables or conductive bars made of electrically conductive material. The electrical installation can be a single-phase or polyphase installation, comprising a number N of electric current phases, with or without a neutral conductor. In the schematic representation of [Fig. 1], the system 2 for measuring electrical quantities comprises a plurality of devices 4 for measuring electrical quantities, for example up to 40 measuring devices. Each device 4 for measuring electrical quantities is connected, in the example illustrated, to an electrical protection device 6, for example a circuit breaker, by means of electrical conductors 8. For example, in one embodiment, all of the circuit breakers 6 and the devices 4 for measuring electrical quantities are placed in an electrical panel or in an electrical cabinet. Alternatively, each device 4 for measuring electrical quantities is connected to a point of the electrical network to be monitored, without connection to an electrical protection device. Each device 4 is provided with a wireless communication interface. In other words, each device 4 is a communicating device, configured to communicate according to a chosen wireless protocol, with the other communicating devices of the system 2 for calculating electrical quantities, thus forming a local communication network of connected objects. For example, the wireless communication protocol implemented is the Bluetooth® protocol, or the Zigbee Green Power ® protocol. As described in more detail below, each device 4 is configured to carry out measurements of electrical quantities characterizing the electrical signal which circulates in the or in each electrical conductor 8 of the electrical installation to be monitored. In particular, each device 4 is configured to provide voltage measurements by capacitive coupling, i.e. without contact with the electrical conductor 8. Thus, each device 4 is a voltage measuring device by capacitive coupling. In one embodiment, each device 4 is further configured to provide continuous electrical current measurements on the or each of the electrical conductors 8 to which it is connected. In other words, in this embodiment, each device 4 is configured to measure current and voltage. In addition, each device 4 comprises a programmable electronic circuit, e.g. a processor, a microprocessor, an electronic circuit formed of programmable logic components, such as FPGAs (Field Programmable Gate Arrays), or even dedicated integrated circuits, such as ASICs (Application Specific Integrated Circuits), configured to carry out calculations of selected electrical quantities. The system 2 further comprises, in one embodiment, a single voltage measurement device 10, called a calibration device, configured to carry out a voltage measurement by contact, provided with a communication interface, so as to allow the broadcasting (in English "broadcast") of the voltage measurements carried out continuously to the devices 4 for measuring electrical quantities, which makes it possible to improve the precision of the voltage measurements in the system. The system 2 further comprises, in this embodiment, a gateway communication device 12, comprising a communication interface 14 configured to communicate according to the communication protocol used by the devices 4, so as to achieve two-way communication with these devices 4. Furthermore, the gateway communication device 12 is configured to communicate, for example according to the same or another wireless communication protocol, with one or more user devices 16. For example, this other wireless communication protocol is the Wifi or Bluetooth® protocol. Alternatively, wired communication is used, for example using the Ethernet or ModBus protocol. Thus, a user, for example a maintenance operator, is capable of receiving, via the user device 16, measurements of electrical quantities obtained, allowing supervision, monitoring of proper operation, planning of predictive maintenance of the electrical installation concerned. The measurements provided are for example displayed on a human-machine interface of the user device 16. The devices 4 for measuring electrical quantities have similar structures, one device 4 for measuring electrical quantities is described in more detail with reference to [Fig.1], it being understood that the other devices 4 are similar. The device 4 comprises a communication interface 20, configured to communicate according to the chosen communication protocol with the other devices 4 and with the gateway communication device 12. The device 4 comprises a module 22 for measuring voltage by capacitive coupling. Several arrangements of such a capacitive coupling voltage module are conceivable and within the reach of those skilled in the art. Thus, the device 4 is a voltage measuring device configured to perform a voltage measurement by capacitive coupling. In addition, the device 4 comprises a calculation processor 24 and an associated clock 26, called the local clock. A dating of an event using the local clock of the device 4 is called dating in the local time frame. Thus, each device 4 has an associated local time reference. The calibration device 10 comprises a communication interface 30, configured to communicate according to the wireless communication protocol with the other devices 4 and with the gateway communication device 12 and a voltage measurement module 32 with connection to the corresponding electrical conductor 8. Advantageously, the voltage measurement module 32 provides a precise voltage measurement in amplitude and phase. The calibration device 10 further comprises a calculation microprocessor 34, or another type of processor, an electronic circuit formed from programmable logic components, such as FPGAs (Field Programmable Gate Arrays), or still dedicated integrated circuits, such as ASICs (Application Specific Integrated Circuit), and an associated local clock 36, which allows dating in a so-called calibration time frame. The gateway communication device 12 also comprises a calculation processor 38 and a clock 40, which is an internal clock of this device, for example associated with the calculation processor 38. One of the communicating devices 4, 10, 12 is selected to fulfill the function of synchronization device, which provides a common time reference frame, called a reference time reference frame. In other words, the synchronization device is the master device of time synchronization, and the other communicating devices in the network are slave devices. In one embodiment, the gateway communication device 12 is chosen as the synchronization device, the clock of this device then being called the synchronization clock, the time reference of the gateway communication device 12 then being the synchronization time reference. Advantageously, the gateway communication device 12 is configured to communicate with all other communicating devices in the system. In particular, when the communication protocol used is the ZigBee Green Power protocol, all communications between communicating devices pass through the gateway communication device, so it is advantageous to select the gateway device 12 as the synchronization device. Alternatively, when the communication protocol is another communication protocol than the ZigBee Green Power protocol, for example the Bluetooth protocol or the ZigBee Pro protocol, another of the communicating devices, for example the calibration device 10 or one of the electrical quantity measuring devices 4 is chosen as the synchronization device. A synchronization mechanism is implemented by the synchronization device and the other communicating devices in the system, allowing each communicating device to date events in the reference time frame. The communicating devices are adapted to receive synchronization messages from the synchronization device, containing so-called synchronization information relating to the synchronization clock. Thanks to this communication, received by each of the communicating devices, it implements a calculation of the time difference between its local clock and the synchronization clock, and consequently, for each local time instant, a corresponding reference time instant. For example, each synchronization message contains an ID number and temporal information, as explained in more detail below. In one embodiment, the synchronization message is broadcast simultaneously to all communicating devices in the network. Thus, the receiving communicating devices receive the synchronization message. In another embodiment, in particular when the communication protocol is the ZigBee GreenPower protocol, the synchronization message is sent to each communicating device in response to a message from the communicating device to the gateway communication device. The synchronization mechanism corrects the offset and drift between the local clock and the synchronization clock, and allows each communicating device to date an event in the reference time frame. An embodiment of the synchronization mechanism will be described below with reference to [Fig.3]. The calibration of the voltage measurements is then carried out in this system 2, to allow calibration in amplitude and phase, the voltage signal being an alternating signal. The calibration device 10, which performs precise measurements, is configured to broadcast in broadcast messages or in messages intended for each device 4, on the one hand the measured voltage amplitude, and on the other hand by a zero-crossing time instant of the voltage signal measured by the calibration device, the time instant being expressed in the reference time frame. These messages intended for calibration are sent regularly, at a given rate, for example every 5 seconds, and more generally at a rate of between 1 second and 30 seconds. More specifically, the calibration device 10 is configured to, during each event Ei of zero crossing of the measured voltage signal: de- end a first reference time instant T-ref;,, in the reference frame reference time, of the event Ei of zero crossing of the signal of measured voltage. issue a calibration message including the first time instant of reference T-ref,, as well as a voltage amplitude value measured towards at at least one device 4 for measuring voltage by capacitive coupling. Each device 4 is configured to determine time instants of passage to Zero of the voltage signal measured locally, in the local time frame, then in the reference time frame, and for: receive the calibration message from the calibration device, and extracting said first reference time instant and the amplitude of tension, determine a second time instant of zero crossing of the signal of voltage measured locally, in the reference time frame, said reference time instant, corresponding to the first reference instant, calculate a phase shift of the locally measured voltage signal, in function of the difference between the first reference time instant and the second reference time instant, apply a voltage calibration in phase and voltage amplitude in function of the received voltage amplitude and the calculated phase shift. In one embodiment, to determine the second time instant corresponding to the first time instant, i, a search is carried out among time instants, in the reference time frame, of zero crossing of the locally measured voltage signal, for example in a range of + / - 1 ms, and it is the time instant closest to the first time instant received which is selected. The estimated phase shift is a time shift between the first and second reference time instants corresponding to the same zero crossing event of the voltage measurement. [Fig.2] graphically illustrates two curves S, and S; in a graph representing the voltage (on the ordinate) as a function of time in the reference time frame (on the abscissa), the curve S, representing the voltage measurement by the calibration device 10 and the curve S representing the voltage measurement by a voltage module of a measuring device 4. The D shift is visible on this graph. With reference to [Fig.3] a synchronization method is described in the case where the communication protocol used by the communicating devices 4, 10 and 12 is the ZigBee Green Power protocol. In this embodiment, the synchronization device is the gateway communication device 12. A particularity of this communication protocol is that communications with the gateway communication device 12 must be initiated by the other communicating devices of the communication network. [Fig. 3] schematically illustrates the synchronization mechanism between the synchronization device 50 (eg the gateway communication device 12) and one of the communicating devices, referenced 52 in [Fig. 3], which may be one of the devices 4 or the device 10. The synchronization device 50 maintains a time synchronization table 54 for each communicating device 52, stored in an electronic memory of the synchronization device 50. The communicating device 52 also maintains, in an electronic memory, a local time synchronization table 56. The example in [Fig.2] illustrates 3 successive communications respectively referenced 53, 55, 57. In this embodiment, the communicating device 52 successively sends messages Mess_1, Mess_2, Mess_3, the content of which is free, to the synchronization device 50. The synchronization device successively sends, in response to the messages Mess 1_, Mess_2, Mess_3 or at regular intervals, synchronization messages M-syn1, M-syn2, Mess-syn3. Each synchronization message contains an incremental identification number, for example incremented by 1 at each sending starting from ID=1 in this example, and time information which is the instant of sending of a previous synchronization message to the communicating device 52. On initialization, the sending time of the previous message is initialized to a predetermined value, for example 0. The synchronization device 50 implements a storage in the time synchronization table 54 of the time instants of sending the synchronization messages, and of the associated incremental identifiers. The time instants of sending are expressed in the reference time frame. The communicating device 52 receives, at reception time instants, in the local time reference, noted T,, the synchronization messages from the synchronization device 50. The communicating device 52 stores the message identifier information and the reception time instant T, in the local time synchronization table 56, as well as the previous message sending time instants received from the synchronization device. The mechanism is repeated in a similar manner during several successive communication steps 53, 55, 57, which makes it possible to store several pieces of time information relating to time instants of sending synchronization messages, in the reference time frame T,1, Ts2, T,3, in the local time synchronization table 56. It is possible to obtain the corresponding time instant T,e:x in the reference time frame for a time instant T,, in the local time frame, from the local time synchronization table 56, it is possible to obtain the corresponding time instant Trçx in the reference time frame. Of course, the method explained with reference to [Fig.3] for a communicating device is applied for each of the communicating devices, i.e. for the calibration device 10 and for each of the devices 4 for measuring electrical quantities. It should be noted that in other embodiments, for example when a communication protocol other than the ZigBee Green Power protocol is used, the messages Mess_1, Mess_2, Mess_3 are not sent. The synchronization device transmits, at regular time intervals, synchronization messages, comprising an incremental identifier and a sending time instant, as explained above. These synchronization messages are used, in a manner analogous to that described above, by each communicating device, to obtain a correspondence between the local clock of the communicating device and the reference clock. [Fig.4] is a block diagram of the main steps of an embodiment of the method for calibrating voltage measurements, comprising a set of steps 100 implemented by the processor of the calibration device and a set of steps 200 implemented respectively by the processor of a device for measuring electrical quantities. The method comprises, for an alternating voltage signal, a step 60 of detecting a zero crossing event Ek, implemented by the calibration device 10, and a dating (step 62) in the local time reference of the calibration device, noted Tm,. In embodiments, detection 60 and dating 62 are performed in a single step. The method further comprises, by the calibration device, a step 64 of determining a first reference time instant T-ref,, in the reference time frame, corresponding to the calibration time instant Tm,, using the synchronization mechanism described above. The method further comprises a transmission 66 of a calibration message comprising the first reference time instant T-ref, and a voltage amplitude value measured by the calibration device to at least one device measuring electrical quantities. The measured voltage amplitude value is, for example, an effective value of the measured AC voltage, also called the root mean square (RMS) value of the measured AC voltage. The device 4 for measuring electrical quantities implements a step 68 of detecting one or more zero crossing events Ej of the locally measured voltage signal, of dating the zero crossing event(s) in the local time frame (step 70), then of calculating corresponding zero crossing time instants, called second time instants, in the reference time frame (step 72) by implementing the synchronization mechanism. In one embodiment, several successive time instants T; of passage to Zero of the locally measured voltage signal are stored in step 72 as well. The device 4 receives, during a reception step 74, the calibration message and extracts from it the first reference time instant calculated by the calibration device 10 and the transmitted voltage amplitude. Then, the device 4 implements a step 76 determining a second time instant of zero crossing of the voltage signal measured locally, in the reference time frame, called second reference time instant T-ref,2, corresponding to said first reference time instant T-ref,., In one embodiment, the second reference time instant T-ref, is the closest zero crossing time instant, among the stored time instants T;, to the first reference time instant T-ref,. For example, the second reference time instant T-ref, ; is offset by less than one millisecond from the first reference time instant T-ref, The method further comprises a step 78 of calculating the phase shift D, as a function of the difference between the first reference time instant T-ref, and the second reference time instant T-ref,2. The calculated phase shift D is then applied to the calibration step 80 to calibrate, i.e. time-reset, the voltage measurements relative to current measurements obtained elsewhere, which then allows a precision power calculation. The voltage amplitude received in the calibration message is also used in calibration step 80 to calibrate the amplitude of the locally measured voltage signal. The steps described above are repeated at regular time intervals, e.g. every 1 to 30 seconds, e.g. every 5 seconds, In one embodiment, the synchronization messages also pass through the gateway device, which transmits them to the electrical quantity measuring devices 4. Advantageously, it is provided, in one embodiment, to group together the calibration and synchronization information intended for the devices 4 for measuring electrical quantities, in synchronization and calibration messages, which makes it possible to reduce the number of messages exchanged, and therefore to reduce the traffic and the energy consumption of the communication modules of the communicating devices.

Claims

Claims

1. DC calibration system for DC voltage measurements in a system measurement of electrical quantities by a plurality of devices measurement of electrical quantities distributed in an installation electric, each device for measuring electrical quantities (4) comprising - a voltage measurement module (22) by capacitive coupling, -a communication interface (20) configured to communicate according to a communication protocol, - a local clock (26) allowing dating of events in a local time frame, the system further comprising a single calibration device (10), configured to measure (32) a voltage signal by contact with one or each electrical conductor of the electrical installation, the device of calibration (10) comprising a communication interface (30) configured to communicate according to said communication protocol and a local clock (36), the system characterized in that it further comprises a syn- device timing comprising a so-called synchronization clock, allowing a dating of an event in a reference time frame, said devices for measuring electrical quantities (4) and the device calibration (10) each being configured to communicate with the synchronization device and to implement a mechanism of synchronization of the local clock with the synchronization clock, allowing dating of an event in said time frame of reference, and in that: the calibration device (10) is configured to: determine a first reference time instant, in the frame of reference reference time, of a zero crossing event of said signal voltage measured by the calibration device, issue a calibration message comprising said first instant reference time and a voltage amplitude value measured towards at least one device measures electrical quantities (4) and, said at least one electrical quantity measuring device (4) is configured for: receive said calibration message from the ca- device libration, and extract said first reference time instant and the voltage amplitude, determine a second time instant of zero crossing of the signal of voltage measured locally, in the reference time frame, said second reference time instant, corresponding to said first reference moment, calculate a phase shift of the locally measured voltage signal, depending on the difference between the first time instant of reference and the second reference time instant, apply a voltage calibration in phase and amplitude in function of the received voltage amplitude and the phase shift calculated.

2. The system of claim 1, wherein said measuring device electrical quantities (4) is configured to store a plurality of second temporal instants, expressed in the reference frame, zero crossing of the locally measured voltage signal.

3. System according to claim 2, wherein for the determination of the second reference time instant, said measuring device electrical quantities (4) is configured to determine among the second stored temporal instants, the second temporal instant of zero crossing closest to said first time instant of reference. |Claim 4] System according to one of claims 1 to 3 in which said device calibration message (10) is configured to broadcast said ca- release to all devices for measuring electrical quantities.

5. System according to one of claims 1 to 4, in which said protocol communication protocol is the ZigBee Green Power protocol.

6. A system according to any one of claims 1 to 5, wherein the synchronization device (12) is configured to send succes- sively synchronization messages to at least one device communicating among electrical quantity measuring devices (4) and said calibration device (10), the synchronization messages- successive synchronization messages including at least one synchronization message current and a previous synchronization message, the syn- current chronology containing an incremental message identifier of synchronization and a time instant of sending the synchronization message- previous nization, each communicating device (4, 10) receiver said synchronization messages being configured to store a local synchronization table, storing information relating to temporal instants, in the local temporal reference frame, of receiving messages from the synchronization device and the moments timescales for sending said synchronization messages, in the re- reference time differential, by the synchronization device.

7. The system of claim 6, wherein each device com- communicant (4, 10) is configured to calculate a correspondence between the local clock of said communicating device and the reference clock using the local synchronization table.

8. System according to one of claims 1 to 7, in which the device of synchronization is a gateway communication device (12), comprising a communication interface (14) configured to com- communicate according to said communication protocol.

9. Method for calibrating voltage measurements implemented in a calibration system according to any one of the claims 1 to 8 including steps: - by the calibration device (10): -determine (64) a first reference time instant, in the re- reference time interval of a zero crossing event said voltage signal measured by the calibration device, - transmit (66) a calibration message comprising said first instant reference time and a voltage amplitude value measured towards at least one device measures electrical quantities (4) - by at least one device for measuring electrical quantities: receive (74) said calibration message from the device calibration, and extract said first reference time instant and the voltage amplitude, determine (76) a second time instant of zero crossing of the voltage signal measured locally, in the time frame of reference, called second reference time instant, corresponding audit first reference moment, calculate (78) a phase shift of the measured voltage signal lo- caly, depending on the difference between the first time instant reference and the second reference time instant, apply (80) a voltage calibration in phase and amplitude in function of the received voltage amplitude and the phase shift calculated.

10. The method of claim 9, wherein said syn- timing involves, by the synchronization device, sending of successive synchronization messages to at least one device com- communicating among the devices for measuring electrical quantities and the calibration device, the successive messages comprising at least a current synchronization message and a sync message- previous nization, the current synchronization message including an incremental synchronization message identifier and a time time of sending the previous message.

11. The method of claim 10, wherein said ca- libration and synchronization are sent by said syn- device timing, grouped into calibration and synchronization messages- nization, intended for said devices for measuring quantities electric.