Figure 7.Disconnected (or weakly coupled)two-area Figure 8.Construction(or expansion)of interconnection system.In standard operational terminology marginal makes it possible to operate the system at lower marginal operating costs are referred to as the systemThe bold costs,resulting in cheaper production costs(that translate and unbold segments are used to designate distinct sup- into end-user electricity rates)for system B without appre- pliers and to emphasize the lumpy nature of the supply ciably affecting the cost of system A. curves.Marginal cost of production and actual conditions can give rise to significantly different marginal operating costs (and consequently significantly different marginal costs of delivering power to customers)in the two systems. System B System A Flow System B High System A Low入 Low7 Low puewog Supply Supply Supply Supply2016/12/22 24