Design of a Synthesized Merging Unit Based on IEC 61850-9-2

To meet the requirements of smart substations for digital information, integrated functions and compact structure, the definitions of merging units in IEC 60044-8 and IEC 61850-9-1/2 were analyzed. Based on the analysis, this paper described a realization of merging units used in the electronic transformers. The hardware and software architectures of merging unit were proposed. According to the design, the merging unit realizes synchronization of sampling pulse, receiving and processing of sampled values, and data transmission. An additional function of phasor measurement was included, which makes it a synthesized device between the process level and the bay level of the digital substation. The data packets were captured and analyzed by Wireshark, corresponding with IEC 61850-9-2, which demonstrates the high flexibility and utility value of the merging unit.