The Research On Merging Unit Technology In 35kV Smart Substation

Under the current national "strong smart grid" development strategy, as the last node of the smart grid substation 35kV substation is a very important part in the power system. It plays a key role in the development of the country’s power industry, in particular to provide a reliable support for the agriculture of power consumption. In order to meet the requirements of intelligent substation in future, the intelligent upgrades for 35kV substation is imperative. As an important digital interface between process level and bay level, the merging unit achieves a voltage and current signals to digital converter transformer output.Firstly, by comparing intelligent substation and traditional substation, this paper figures out the importance of merging unit in intelligent substation. According to IEC61850 standard intelligent substation construction, this paper offers a design scheme based on ARM+FPGA which is applicable to the merging unit in 35kV intelligent substation. And according to characters of 35kV substation and merging unit’s technical standard, this paper researches three functional modules of merging unit, including data receiving and processing module, data synchronization module and data communication module. Fourthly, from analog signal’s current-voltage conversion, analog small signal’s amplification, A/D conversion, digital filtering, GPS second pulse synchronization, optical port and electrical port conversion, Ethernet message sending and other functions, implements merging unit three functional modules. Finally, experimental test is carried out for each module. Experimental results show that this design of the merging unit is correct and feasible. Each functional module’s performance meets the technical requirements. Sample values’ frames packaged by IEC61850-9-2LE standard are sent correctly on Ethernet.Based on the long-term coexistence of electronic transformers and conventional transfers which is current situation of large number of 35kV substation, this paper offers a design of merging unit for 35kV substation. The unit provides data interface between conventional transformers and electronic transformers, and GPS second pulse synchronization is used to handle problems with clock sync. Using digital method, implementation upgrading of 35kV intelligent substation has an important significance to 35kV substation’s intellectualization construction.