This paper explores the relationships between power system static collapse and flows in topological cuts. It seeks a "local" detection of this "global" phenomenon. The paper proposes a method capable of identifying a limiting cut which has this property. This method is based on the concepts of "bus through flow" and a bus static transfer stability limit (BSTSL), both defined here. Exploration of the limitations of power transfer through buses and topological cuts provides insight on the mechanisms for static collapse and points to remedial actions to extend its margin.