• It is essential
to create a tertiary layer for monitoring tie-line flows and regulating these according to the well-defined interconnection criteria (this is important for
1) ensuring feasible
scheduling of power exchanges; 2) communicating change of major equipment status; 3) preventing slow inter-area oscillations; and 4) implementing open access for economic reasons w/o endangering system reliability;
•At the same time, the design must be done so that each layer keeps its
decentralized, autonomous decision making,
while coordinating with the higher layers.