New application of graph theory to the topological analysis of protection schemes

Abstract

Modern power system networks often consist of multi-loop structures. The coordination of protective relays in such networks is an iterative and time consuming process. To minimize the number of iterations, a proper set of relays, referred to as Break Point Set (BPS), with a minimal size is required to start the coordination procedure. This paper presents a new graph-theoretical method for the BPS determination. The method represents the primary/backup relation among relays by a directed graph, referred to as dependency-diagram. This representation converts the BPS determination to a problem of graph theory. The method approaches step by step to a minimum and/or a near-to-minimum BPS, choosing the best break point relay at each step. The graph-theoretical rules of the method exploit the sparsity of the relations among the relays and reduce the complexity of the problem. Due to the generality of the method, it can be easily applied to any protection schemes and network configurations.