## 6 Conclusions  
As intermittent distributed energy resources such as photovoltaic power generation are widely connected to the distribution network, the power quality, as well as the safe and reliable operation of the distribution network, face new challenges. Wide area measurement control and protection technology based on a synchronous clock is an important and effective means to solve related problems. In the distribution network, WAMS technologies are mainly used for protection and active control. The WAMS shares the communication channel with the distribution automation system. The IEC 60870-5-101/104 protocol of the distribution network SCADA is integrated into the WAMS communication protocol, thereby increasing the functionality and efficiency of the WAMS communication protocol and distribution automation systems, enhancing the ability of the traditional distribution network to absorb intermittent distributed energy resources, improving the reliability and power quality of the distribution network. The main conclusions of this paper are as follows:  
* Based on the analysis of the communication requirements of the active distribution network, this paper compares the distribution network SCADA and the transmission network WAMS, and obtains the application scenarios, functions, and performance requirements of the uMPMU;
* The GB/T 26865.2-2011 and IEC 60870-5-101/104 protocols are compared. By analyzing the applicable parts of each protocol on the uMPMU, a priority-based synchronization phasor transmission protocol expansion method for active distribution networks is proposed;
* The method is based on the existing GB/T 26865.2-2011 protocol, and refers to the Application Service Data Unit (ASDU) of IEC 60870-5-101/104 to add an application extension frame, which increases file types, divides the data priority, increases communication processes, such as total summoning and remote control, and gives data flow calculation methods;
* The uMPMU multi-priority data processing model was proposed;
* The experimental environment is built using the self-developed PMU Emulator, distribution network PDC, and Main station Emulator. Some technical details of them are introduced;
* By running the standard GB/T 26865.2-2011 protocol and extended protocol, the effectiveness of the method in reducing the amount of communication data, the effectiveness of the data prioritization model and the implementation of the remote control function are verified;
* The calculation results of the file storage also indicate the effectiveness of the method in reducing the amount of stored data.  
Figure 16: Field installation diagram. (**a**) Front side; (**b**) back side wiring.  
The phasor transmission protocol GB/T 26865.2-2011 and IEEE C37.118.2-2011 are Chinese standards and international standards, respectively, which have basically the same message structure and communication process. The method in this paper is easy to use for the integration of IEEE C37.118.2-2011 and IEC 60870-5-101/104 protocols, so that they can both be used in distribution network WAMS in other countries and regions. Further work of the author's team will use compression techniques for phasor transmission and waveform file transmission, so that the distribution network WAMS can communicate more efficiently using the LTE 230 MHz wireless power private network and the broadband power line carrier.  
The contribution of [PERSON] was reviewing and editing; the contribution of [PERSON] was writing the original draft, reviewing, and editing; the contribution of [PERSON] was reviewing and editing; and [PERSON] and [PERSON] contributed to finalizing this paper.  
This work was funded by The National Key R&D Plan of China, grant number 2017 YFB0902800.  
The authors declare no conflict of interest.