A case study serves in making the picture clearer to the reader. This case study covers an expansion in the generation area of a real life electric power system.
TopGeneration Expansion
Power system expansion plans are determined through studies, which are basically analyses of future plant additions required to meet expected demand. The output of such studies is an investment plan detailing the size, type, location, and capital as well as O&M costs of generation and T&D plants (Dhadbanjan & Chintamani, 2009; Kamyab, Fotuhi-Friuzabad, & Rashidinejad, 2008).
Expansion plans are usually carried out for 20+ years. They may be updated every year to reflect any changes or modifications on demand forecast due to unforeseen changes in the driving forces for electricity demand. In developing countries, such unforeseen changes may be the norm. This is due to the fact that demand is still evolving and has not yet reached a case of saturation or maturity like in developed countries. Therefore, in developing countries expansion studies are repeated more often and in some countries they are carried out every year. Fortunately there are software packages which make life easier. It is only natural that planning criteria are revised whenever a new expansion study is needed.
Expansion studies, therefore, are simply an attempt to match future electricity supply to future demand with certain constraints imposed by the status of the power system, and financial and other considerations. Planning criteria on the other hand are self-imposed conditions to narrow the selection process (Park, et al., 2000)
The expansion study is somewhat a search for an optimum least-cost investment program, which satisfies the future demand, any specified constraints and falls within the defined planning criteria.
The objective function of the expansion problem is therefore (IAEA, 1984):
(9.1) Where: