The PDC can then either request the header frame or turn on the data transmission, in this case it chooses to request the header frame, PMU sends it. The standard does not have an example for this frame, so it was structured for the purposes of the example. In this frame, the PMU_AXON message is sent as shown in Figure 4.
Upon receiving it, the PDC sends the command to start data transmission. At that moment PMU starts sending data frames at the reporting rate indicated in the configuration frame, 30 fps. In the real case, in the simulation, frames are sent manually using Hercules. In this example, four data frames are sent.
As shown in figure 5, in the first data message 4 phasors are sent, 3 voltage and one current, the frequency, the ROCOF, the analog and the digital words. The PMU stops sending data until the PDC sends the command to turn off the data transmission
The synchrophasor communication protocol is designed so that technologies that process information from synchrophasors do not have to perform complex processes that delay the transmission of information. The main advantage of synchrophasor systems is their high real-time reporting rates of up to 60 messages per second, and that each transmitted message comes with an assigned timestamp thanks to the synchronization of the PMU with the GPS system. With these timestamps it is possible to identify the exact place and time when an event occurred on the power grid.
Article written by: Juan Carlos Vargas, Axon Group