Research On Complex Fault Diagnosis Of Multi-area Power Systems

Power system is a key infrastructure and blackouts have major direct and indirect consequences on the economy and national security. But blackouts caused by accidents can not be avoided completely. It is not very practical for the operators to judge the blackouts immediately and take exact measures to reduce the loss as soon as possible only by experiences. Moreover, the interconnection of power system adds to the difficulties of monitoring and control. Single fault sometimes spreads in the whole system and results in serious blackout. Hence, it is more important to monitor, trace and give early-warning of faults in power grid.In this dissertation, complex fault diagnosis of multi-area of power system is studied along with three coordinates: fault diagnosis method, operational defence and system modeling. The main content includes: the method of identifying original faults, the uncertain fault diagnosis method of handling the alarm messages of mal-operation or failure to trip of the protection relay and breaker, the technology for fulfilling the cooperation and separating rule base with the system based on BNF and its assistant tools. The cooperative fault diagnosis method integrates the methods and technologies into a unit scheme, and realizes the fault diagnosis and operational defence of the power system.Main contributions of this dissertation are stated as below:1) The literatures about fault diagnosis of power system are investigated and summarized; the advantages and disadvantages of the main diagnosis methods are analyzed;2) Based on knowledge expression and algorithm of the logic inference, bidirectional deduction system which combines the logic inference with the rule-based inference is applied for identifying original faults. The fault is diagnosed through rapid logic inference first, then through rule-based inference farther.The forward deduction system is introduced in detail, and the simulating result shows that the method is correct and useful. An operational defense method based on dynamic deduction system which can put forward the operational advice according to the fault diagnosis results is flexible and economical.3) Considering the fault diagnosis becomes more complex due to the uncertain fault alarm messages caused by the mal-operation or failure to trip of the protection relay and breaker, a fault diagnosis approach based on Bayesian network and MCMC (Markov Chain Monte Carlo Method) method is proposed for fault diagnosis in a large scale power system. It makes a diagnosis model based on two foundational models of Bayesian network, and uses MCMC reasoning method. With the capacity of revealing relationships among data in the models and analysis the probabilities of...