Thesis (Ph.D.)--Chulalongkorn University, 2010

This dissertation proposes a Benders decomposition based method for solving a multistage transmission expansion planning (TEP) problem with security constraints. An AC model is used to develop the TEP problem instead of a DC model, which is generally used in previous research works. With the proposed method, the TEP problem is decomposed into an investment and operation problems. An optimum plan can be obtained by iteratively solving both problems. In addition, the generation cost is taken into account, which results in active power loss decrease and transmission congestion alleviation. The proposed method has been tested with 6-bus Garver, IEEE 24-bus and 75-bus northeastern Thailand systems to demonstrate its capability of solving various sizes of the problems. With the obtained results, it shows that the proposed method can be applied in actual transmission system planning.