The Research Of The Smart Terminal And The Merging Unit In The Digital Substation

At present, the research and construction of digital substation have become the developmental trend of transformer substation. The development of digital substation has been restricted because of the technology instability and high cost of electronic transformer. The digital transformation in traditional substation has great research value and marketing value. This paper presents the research of the structure and the communication mode of the digital substation system. The system of the smart terminal and the merging unit are designed. The new digital substation system SDP9000 is constructed which can collect and process the traditional current and voltage transformer, realize the digital transformation in traditional substation in the high reliability and low cost.According to functional requirements of the smart terminal and the merging unit, the research and design of the smart terminal and the merging unit is made from the two aspects of software and hardware. The smart terminal adopt high speed digital processor TMS320F2812 as the main controller chip and choose a high speed, high accuracy A/D conversion chip to realize collection and digitizing of the analog values of traditional electromagnetic transformer substation. The optical fiber communication technologies are applied to achieve high speed transmission and low interference for acquisition data. The mixture programming of the c language and the assembly language programming is used at the smart terminal and modular design is also adopted to achieve the convenience of improvement and expansion of the system. FPGA and TMS320F2812 build up the core processor of the merging unit. FPGA is the data receiving processor of the merging unit which can realize the high-speed parallel processing of upload data at the smart terminal. It can increase the ability of the serial data processing. TMS320F2812 has been used to realize the Ethernet correspondence of the merging unit and the secondary protection devices. They runs together in order to reduce the fault response time of the relay protection system for substation and improve the performance of SDP9000 digital substation system.This communication solution between the smart terminal and the merging unit in this digitized substation system is discussed. The protocols of the network communication of the merging unit and protection equipments are proposed and it is used to realize the application of the IEC61850 in the SDP9000 digital substation system.Finally, the OPNET network simulation software is used to achieve the Ethernet communication between protection equipment and the merging unit. The results of simulation show that this digital substation system completely satisfies the specific requirements of the response time.