The IED's Process Level Interface Technique Of Substation Based On SoPC

With the application of new substation equipments (e.g., electronic transformer, intelligent breaker) and the publication of IEC 61850 stardand, the substation automation system (SAS) is undergoing revolutionary change. The way for substation IED to obtain secondary voltage, current and swich status changes from sampling secondary signals directly into receiving process level serial data. Therefore, the research on IED's process level interface (PLI) technique is very important to develop IEC 61850 compatiable IED and to promote the development of substation automation technology.This paper analyses the problems of the existing SAS and points out the implementation of IEC 61850 standard, which can realize interoperability and data sharing among IEDs and slove "island of automation", is the trend of substation automation technology. With the detailed study and analysis to IEC 61850, the essential contents and core technique are summarized. The IEC 61850-9 standard which related with IED PLI technique is researched emphatically and the contents of data frame of process level communication are studied. 3 modes of IED PLI cuicirts for receving sampled values are proposed, i.e., direct receiving-processing mode, analog signal regeneration mode and receiving -retransmitting mode. The advantages and disadvantages of the 3 modes and their applications are analyzed.Based On the analysis of process level communication technique, the design sheme of PLI data reveiving-retrasmitting circuit using SoPC is presented. It receives the data packet of process level communication channel, sustracts the sampled values and forwards them to DSP/MCU for further processing. The circuit acts as signal conditioning and A/D circuit in conventional IED and can be used easily to convert the transitional IED into a IEC61850 compatiable one. The Ethernet interface circuit using LAN91C111 chip is designed and the NiosII soft core andμC/OS-II RTOS (Real Time multi-tasking Operation System) are emulated. Using the Altera development board, the data receiving module, which is a function of the circuit, is realized. The test result proved the design scheme is feasiable and the data receiving module works reliably. The works done and results achived is valueable to the development of substation IED and application of IEC61850 standard.