An application of functional dependencies to the topological analysis of protection schemes

The concept of functional dependency is applied to the problem of relay coordination in protection systems. An algorithm is developed for the identification of a minimal break point set (BPS) of relays of a protection topology. This algorithm is an improvement over existing algorithms in that it identifies a minimal BPS within a time period that is a polynomial function of the number of relays, while the earlier algorithms had exponential time behavior. In the case of large protection schemes, the saving in computation costs is considerable. An algorithm is developed for the selection of a relative sequence matrix; this algorithm also has polynomial time complexity. The functional dependency approach is seen to be more flexible and more powerful than the graph theoretic schemes, and holds out much promise for the development of efficient computer-aided design tools for the protection engineer