Study On Communication Module Of Electronic Current Transformer

With the development of power system towards extra high voltage, highercapacity and digitization, electronic current transformer substituting the oldelectromagnetic current transformer is unavoidable. Because it is very differentin output form between electronic current transformer and traditionalelectromagnetic transformer, how to select and design the interface between theprocessing level and the bay level in substation becomes the key problem ofresearch. According to IEC60044-8 standard, the realization methods of thedigital output for electronic current transformer is researched in the thesis, andthe major topic concerns the digital signal processing module of processing level,the encoding module of processing level and the decoding module of bay level.The function of the digital signal processing module of processing level isto complete collecting and decimating filtering the multi-channels data fromelectronic transformer. A new method to synchronize data among Merging Unitfollowed by IEC60044-8 is discussed in this paper, and the efficient algorithmfor decimating filtering is analyzed and applied in FPGA by programming withVHDL. Because the FPGA has high integration and flexible programming, thereal-time property and reliability of the system are ensured. At the encodingmodule of processing level, the frame head and CRC code are appended to thedata which is decimated to complete framing, then the total data frame isencoded on Manchester code and is transmitted to bay level using fiber based onthe standard. The circuit of encoding module is designed in detail and isanalysed with comparing in this paper. At the bay level, based on All-DigitalPhase-Locked Loop technology, the circuit of decoding module is designed byusing the characteristic that Manchester code has rich bit timing information initself, and it is used to collect these high speed data stream and synchronize toincoming serial data stream in order to decode the data, then unpack the dataframe and check. By the research in this thesis, the digital communicationbetween the processing level and the bay level is realized, which can providesome experience for application of electronic current transformer in substationautomation system.