Process Bus Of Digital Substation Based On Peer To Peer Communication

With the application of new substation equipments (e.g., electronic transformer, intelligent breaker) and the publication of IEC 61850 standard, the age of digital substation is coming. In digital substation, primary voltage, current and switch status are transmitted via Ethernet with the form of digital signals. So, the research on substation process bus communication (PBC) technique is very important to develop IEC 61850 compatible digital substation system and to promote the development of substation automation technology.From the summarization to the existing substation PBC technique, it is obtained that the sampling transmission mode based on IEC 61850-9-1 has shortages and is limited in the application.The function and structure of substation automation system (SAS) is introduced firstly. Then based on digital substation, the technical characteristics of digital substation are analyzed thoroughly. The basic philosophy and core technique of IEC 61850 standard are introduced in detail. The domestic and foreign application of IEC 61850 is summarized. With the introduction to the concept and characteristics of peer-to-peer communication, the sampling transmission and GOOSE information transmission which both employ peer-to-peer communication mode are researched thoroughly. In terms of sampling transmission model and sampling value control block (SVCB), the two different service mapping modes of sampling transmissions which are defined separately by IEC 61850-9-1 and IEC 61850-9-2 are researched in detailed.IEC 61850-9-2 can suppose bidirectional transmission, and the sampling information and sampling rate can be configured freely, which satisfy the requirement of digital substation.Based on GOOSE information transmission model, GOOSE control block (GoCB) and service mapping mode of GOOSE information transmission are provided.The information modeling to PBC system of digital substation is finished and the services supported by the model are provided. Taking the low voltage bay of an 110kV substation as the object, the block is abstracted in terms of functions, and classified to four levels: logic device, logic node, data and data attribution. Firstly, two logic devices are modeled—the merging unit which transmits the sampling value and state variable to IED of bay level and the switch control unit which transmit control command to breakers and disconnected switches. Then logic node zero, logical node physical device and other logic nodes are modeled for the two logic devices. The data, control block and data set corresponding with the control block are also provided.The data attributes are listed and the information models of sampling data set are given. Lastly the mapping modes of the sampling value and control information modeled in this paper are provided.IEC 61850 is very important to the development of digital substation system. The direction of PBC technique is the combination of the sampling transmission mode based on IEC 61850-9-2 and the GOOSE information transmission mode. The work completed and results are valuable to the development of PBC in digital substation system.