Application of substitutability in congestion relief

The principal cause of transmission congestion is the lack of adequate transfer capabilities in the network. A modification of the network resulting in the increase of the constrained transfer capability(ies) is a viable scheme for congestion relief. An alternative approach is the addition of supply sources at nodes at which additional injection can be accommodated without violating the network constraints. In this sense, we may view the generation resource addition (GRA) and the transmission transfer capability enhancement (TCE) as substitutable congestion relief schemes. In this paper, we define and quantify the notion of substitutability in terms of the impacts of the GRA and those of the TCE on the electricity market outcomes. We use the social welfare as the metric to quantify the impacts of the modification of the resource mix or of the network. This measure allows the quantification to be performed on a consistent basis. We derive criteria under which the GRA and the TCE are substitutable for congestion relief. Simulation results on various test systems indicate the comparative ability of attaining congestion relief through a GRA or a TCE. Illustrative results on the IEEE 57-bus network are provided.