Possibilistic-diagnosis theory for fault-section estimation and state identification of unobserved protective relays using tabu-search method

In the paper an integrated approach is presented for fault-section estimation and state identification of those protective relays whose state information is not available in electrical power dispatching centres (hereafter the authors refer to these protective relays as unobserved protective relays) using tabu-search (TS) method. The proposed fault-section estimation method utilises incomplete operational information of protective relays and tripping information of circuit breakers, and is able to deal with the operating reliabilities of protective relays and circuit breakers. At first, based on the logic relationship among section fault, protective relay operation and circuit breaker trip, a 0-1 integer programming model for fault-section estimation and state identification of unobserved protective relays (FSE-SIUPR) is presented. The developed model is based on recently proposed possibilistic-diagnosis theory under graded uncertainty and the well developed parsimonious set covering theory. In this model, the problem of the fault-section estimation under incomplete information from protective relays is dealt with in a formal and systematic manner, and the operating reliabilities of protective relays and circuit breakers are taken into account at the same time. Secondly, the TS method is used to solve this 0-1 programming model to find the optimal solution efficiently. In addition, an efficient method for identification of faulty subnetworks which include all faulty sections is adopted by using the real-time information from circuit breakers. Extensive test results of a sample power system have demonstrated the correctness of the developed mathematical model and the efficiency of the TS-based method.