The Research On Reliability Of Digital Substation Relay Protection System

With the progress of science and technology, substations are changing gradually into the direction of digital and intelligent in their information collection, transmission and processing. Information technology and network communication technology are constantly applied into every aspect of substations, especially that the promulgation and implementation of the IEC61850standard provide technical support and advancing direction for them. On the way of digitalization, substation has changed deeply in its relay protection system in structure and connotation. Compared with traditional ones, digital relay protections add many new elements, which make it uncertain whether they can operate stably. Thus how to evaluate the reliability of relay protection systems in digital substations is an issue that worth studying.Based on the study of characteristics of digital substation technology and composition mode of relay protection system, this essay uses minimal path sets algorithm based on Reliability Block Diagram analysis method to establish reliability evaluation model which takes time synchronization message flow, SV message flow and GOOSE message flow as target. This model can reflect clearly the influence on the reliability, which made by different kinds of structures and composition of relay protection systems. It can be used to distinguish which kind of the organization form of the system is the best one from the possible alternatives. Since it is difficult to handle with large systems by using this model with hand computation, we choose the idea of computer programming. The program uses node traversal algorithm and disjoint calculation algorithm, and it can solve the reliability of any kind of structure of digital relay protection systems by using computers, which has greatly improved in speed and accuracy.The method above presents a reliability calculation model for hardware structure of relay protection system. Except that we also give a summary of software factors which may influence on reliability. It together with hardware reliability provide a train of thought to evaluate relay protection systems.