## 2 Active Distribution Network Communication Demand Analysis
### The \(\mu\)MPMU Application
\begin{table}
\begin{tabular}{c l l} \hline \hline  & **Supervisory Control and Data Acquisition (SCADA)** & **Wide Area Measurement System (WAMS)** \\ \hline \multirow{2}{*}{Function} & Basic telecontrol task, energy accumulation transmission, relay protection equipment control & Global Positioning System/BeiData Navigation Satellite System (GPS/BDS) time, phasor measurement, high precision simultaneous sampling \\ \hline \multirow{4}{*}{Application} & State estimation, load forecasting, online trend and security analysis, automatic failure analysis, prepared from the cast, sensitivity analysis, secure analysis, system dynamic behavior monitoring, dynamic load behavior monitoring, voltage stability monitoring, regional stability control, online transient stability monitoring, failure analysis \\ \hline \multirow{2}{*}{Protocol} & International Electro technical Commission (IEC) 60870-5 series & National Standard of the People’s Republic of China/Recommended (GP/T) 26865.2-2011 \\ \hline \multirow{2}{*}{Communication method} & Serial communication & Network communication \\  & IP-based network communication & IP-based network communication \\ \hline \multirow{2}{*}{Communication medium} & Optical fiber, wireless private network, power line carrier, wireless public network & Optical fiber \\ \hline \multirow{2}{*}{Communication mode} & Polling & CDT \\  & Cycle distance transmission (CDT) & Publish/subscribe mode \\ \hline \multirow{2}{*}{Data} & Telemetry data, telesignalization, cumulative amount, remote control information, files, time synchronization & Status, phasor, frequency offset, frequency change rate, analog, digital, configuration information, command, files \\ \hline \multirow{2}{*}{Data transmission} & Second level & Millisecond level \\ \hline \hline \end{tabular}
\end{table} 
Table 2: System function comparison. 2. The uMPMU should be smaller than the main network PMU, and the size should be selected based on the installation location. For example, the uMPMU mounted on the pole (which refers to the FTU mounting position) should be smaller than the uMPMU installed in the sub-section post (which refers to the DTU mounting position). The choice of communication medium is more diversified, and communication media may include the optical fiber, wireless private network, power line carrier, etc., and the communication delay under various combinations should be less than 150 ms;
3. The uMPMU acquisition quantity should include a three-phase voltage, three-phase current, zero-sequence current, analog quantity, switching quantity, etc., and has the basic three-remote function of the distribution network terminal. The phasor data transmission rate is 25, 50, and 100, frames/s optional;
4. WAMS has always had the problem of a high communication delay and massive data processing. For the application of uMPMU to the distribution network, with a greater number of uMPMU, more data will be generated. It is, thus, necessary to solve the problem of high communication delay and massive data processing. In conclusion, in addition to improving the processing capabilities of hardware devices, the communication protocol should also be re-optimized [26]. Figure 1 shows the distribution network WAMS organizational structure, which can share the communication network with the existing distribution terminal. Substations communicate with the power distribution main station via the backbone communication network, and the backbone network is based on Synchronous Digital Hierarchy/Multi-Service Transfer Platform (SDH/MSTP). The communications between the distribution line uMPMUs and substation PDCs are located at the access layer. There are a variety of communication methods, including Ethernet and passive optical networks based on fiber-optic communication, and wireless private networks based on 4G LTE 230 MHz. Individual isolated points can also consider the use of Orthogonal Frequency Division Multiplexing (OFDM)-based broadband power line carrier communication. Figure 1: Distribution network WAMS organizational structure.