Method and system for calibrating voltage measurements in a system for measuring electrical quantities

A system for calibrating voltage measurements in a system for measuring electrical quantities by means of a plurality of devices for measuring electrical quantities which are distributed in an electrical apparatus,

• each of the plurality of devices for measuring electrical quantities comprising:
• a module for measuring voltage by means of capacitive coupling,
• a communication interface configured to communicate according to a communication protocol,
• a local clock configured to date events in a local temporal reference frame,
• the system further comprising a single calibration device configured to measure a voltage signal by means of contact with an electrical conductor of the electrical apparatus, the calibration device comprising a communication interface configured to communicate according to the communication protocol and an associated local clock,
• wherein the system further comprises a synchronization device comprising a synchronization clock configured to date an event in a reference temporal reference frame, the synchronization device configured to:
• send successive synchronization messages to at least one communicating device from among the plurality of devices for measuring electrical quantities and the calibration device,
• wherein the successive messages comprise at least a current synchronization message and a preceding synchronization message, the current synchronization message comprising an incremental synchronization message identifier and a time instant at which the preceding message is sent,
• wherein each of the plurality of devices for measuring electrical quantities and the calibration device is configured to communicate with the synchronization device and to implement a mechanism for synchronizing the local clock with the synchronization clock, to date an event in the reference temporal reference frame, wherein the calibration device is configured to:
• determine a first reference time instant, in the reference temporal reference frame, of a zero-crossing event of the voltage signal measured by the calibration device,
• transmit a calibration message comprising the first reference time instant and a measured voltage amplitude value to at least one of the plurality of devices for measuring electrical quantities, and
• wherein the at least one of the plurality of devices for measuring electrical quantities is configured to:
• receive the calibration message from the calibration device, and extract the first reference time instant and the measured voltage amplitude,
• determine a second reference time instant, in the reference temporal reference frame, of a zero crossing of the voltage signal measured locally the second reference time instant corresponding to the first reference time instant,
• calculate a phase shift of the locally-measured voltage signal, as a function of a difference between the first reference time instant and the second reference time instant, and
• apply a phase and amplitude voltage calibration as a function of the received measured voltage amplitude and of the calculated phase shift.