Contingency constrained economic dispatch algorithm for transmission planning

Planning the long-term development of the CEGB's power system requires an economic assessment of alternative investment options. These may involve examining the economic consequences of different power station siting proposals, and/or of alternative transmission reinforcements. In either case it is necessary to estimate the economic savings which would accrue from different options. Previous CEGB planning tools using boundary constraints have not been sufficiently sensitive to the transmission network and its line limits for this to be done accurately but advances in economic dispatch algorithms in recent years now make this possible. For this purpose, an operational model has been developed which performs an economic dispatch of active power subject to transmission limits and contingency constraints. An iterative procedure permits the nonlinear transmission losses to be optimised efficiently by a linear program, enabling the savings in out-of-merit generation and transmission losses to be predicted accurately for a proposed trans mission reinforcement. The size of the linear program is minimised by keeping only one active generator per node and considering only the small subset of constraints that is near-critical. These efficiency benefits are achieved without loss of optimality.