## 5 Experimental Verification
### Experimental Results and Analysis  
Five PMUs are run on the PMU Emulator. Each PMU is configured with 8 phasors, 42 analog quantities, and 16 digital quantities. First, the standard GB/T 26865.2-2011 protocol is run. The PDC  
Figure 9: Experimental environment. establishes a communication connection with each PMU in the PMU Emulator. The data frame rate is 100 frames/s, and the Main station Emulator is then connected to the PDC. The running result on the main station side is shown in Figure 10.  
In Figure 10a, the traffic statistics are shown, and the change in traffic can also reflect the communication process. Because all pipelines are based on TCP, the filter condition selects TCP. The data traffic from both the data pipeline and the management pipeline are counted. The horizontal axis is the X-axis, which indicates the time, with a scale unit of 0.1 s. The vertical axis is the Y-axis, with a unit of bytes/Tick, and a scale of 10,000. Peak (1) shows the traffic generated by the CFG1 of the PDC actively summoned by the main station. The PDC aggregates CFG1 of each PMU to generate its own CFG1. Peak (2) depicts that the main station delivers the traffic generated by CFG2. Peak (3) indicates the traffic generated by the PDC uploading the data frame after the PDC starts the real-time data transmission. Figure 10b illustrates more details of data frames. The first column \"No.\" indicates the serial number of the frame. The second column \"Time\" indicates the time of the frame's issuance or arrival, the unit is in seconds, and the time when the packet capturing starts is set to 0. The third column \"Source\" indicates the source address. The fourth column \"Destination\" indicates the destination  
Figure 10: Standard GB/T 26865.2-2011 protocol operation results. (**a**) Communication data traffic; (**b**) data frame. address. The fifth column \"Protocol\" indicates the selected transport layer protocol. The sixth column \"Info\" shows more information about the packet. User can view the details of the packet from below. It can be seen that the time interval of data frames is uniform, at 10 ms, and the length of each data frame is 642 bytes, which contains data of five PMUs. Data frame SYNC is 0 xaa03. In both Figure 10a,b, filter conditions are tcp, statistics data frames, and TCP acknowledgement packets data traffic to more accurately reflect the traffic generated by running the protocol. In the next run for the extended specification, the number of PMUs is unchanged, but each PMU retains all phasors and two analog quantities in data frames for transmission, and the remaining 40 analog quantities and all digital quantities are transmitted in application extension frames. These analog and digital quantities are configured in the device's initialization point table and are not transmitted in CFG1 and CFG2. The transmission period of application extension frames, which contain analog and digital quantities, can be modified. Here, we choose 2 s and 5 s as the transmission cycle in turn. After starting the communication, the running result on the main station side is shown in Figure 11.  
Figure 11: _Cont._  
Figure 11a,b shows data traffic statistics, and the parameters of the coordinate system are the same as those of Figure 10a. Peak (1) shows the traffic generated by the CFG1 of the PDC actively summoned by the main station. Peak (2) depicts that the main station delivers the traffic generated by CFG2. In response to the total summon, Peak (3) indicates the traffic generated by the PDC uploading application extension frames with digital quantities. Peak (4) illustrates the traffic generated by the PDC uploading application extension frames with analog quantities. The interval between the two types of data is 1 s. Peak (5) indicates the traffic generated by the PDC uploading the data frame after the PDC starts the real-time data transmission. After the real-time data transmission is enabled, a command is issued to start the periodic transmission of application extension frames.