The Study On The Communication System Of Integrated Protection In A Digital Substation Based On IEC61850

In recent years, the dramatic growth in signal processing power in relay platforms, and the availability of widespread communications schemes, has provided new opportunity to study the concept of integrated protection.The integrated protection which is a new concept designed for a digital substation integrates many protections into it, such as line protection, transformer protection, busbar protection, etc. It is different from conventional substation protection. The communication process for a digital substation has achieved absolute digitization on which new means of integrated protection based. The new means are provided for processing digital quantity. According to integrated protection, different protection may share the same data or the processing consequence by other protections, a large number of digital quantities will be exchanged. Not only the raw data which is collected by the mutual inductors and processed by the merging units, but also the communication between the process level and bay level, require digitization should be the basis of achieving integrated protection. Since the analog quantity is transformed into digital quantity by primary devices, the number of the digital data has been very large. Meanwhile, the digital data will be output by merging units and exchangers which are the devices in process level, then the data will be sent to the integrated protection in bay level for being processed. In order to reach the requirement for real-time and security, the data stream needs a communication system as a platform for realization in the digital substation.This paper will firstly introduce the communication part of IEC61850, and the application of frame format for Ethernet will be given. Then a whole plan for the communication system of a digital substation is designed. To abide by IEC international standard about substation communication network and system, the paper presents a structure based on the concept of object-oriented hierarchical distributed design. Based on the proposal, there are three major components within the network:the station layer, interval layer and process layer.This paper investigates an advanced substation communication system to meet the requirements of the latest development of power system protection, the integrated protection. The paper focused on the main components and the functions realization of the communication network which supports integrated protection. It also discusses the requirement of a digital substation for real-time, security and reliability. Studies have suggested that the new communication network is not only very significant to the integrated protection, but also to the future development of power system protection.