New graph-theoretical scheme for coordination of protection systems: Determination of Break Point Set

Abstract

The basic task of a electrical power system protection is to detect faults in system components, and to rapidly isolate them by opening all incoming current paths. On the other hand, in the case of any fault, the protection system should disconnect only a minimum number of components, to minimize interruptions to consumers. Therefore, relays of a protection system should be adjusted for the minimum possible operation time, while maintaining coordination among all relays. Modern power system networks are often multi-loop structured. Coordinated setting of protective relays in such networks is tedious and time consuming. The complicated part of this problem is the determination of a minimum set of relays, the so-called minimum Break Point Set (BPS), to start the coordination procedure. This report presents a new graph-theoretical method to determine a minimum or a near-to-minimum BPS. Using the rules of this method, the determination of a minimum BPS can be reduced and decomposed into sub-problems. Owing to the efficiency of these rules, the presented method quickly achieves the result, even for large networks. Moreover, due to the simplicity of the method, it can be manually applied to the graph of each network. Since the presented rules are general, they can be applied to improve any method dealing with BPS determination.