Transmission system planning is conventionally carried out based on the present system configuration and under the future supply and demand condition. This paper proposes a methodology to design a transmission system configuration on a greenfield [1] where the present configuration is neglected but only land condition, generator condition, load condition, and acceptable reliability are considered. Several voltage levels are available as candidates to obtain the minimum transmission cost. Transient stability constraint is also considered to ensure that the system can withstand sudden large disturbances.