Flexible AC Transmission System (FACTS) devices are used in to improve stability and loadability of transmission networks as well as minimise losses. Types of FACTS that are normally used are Thyristor Controller Series Compensator (TCSC) and Unified Power Flow Controller (UPFC) which is to control power flow and stability of the power system at a certain location. The TCSC is suitable because it can be installed in a long transmission line system while UPFC can solve any reactive power problems. The objective of this study is to minimise total power losses and to improve the voltage profile by using FACTS devices in the transmission system. This paper proposes a static voltage stability index (SVSI) to determine the size and placement of TCSC and the Evolutionary Programming (EP) technique. The results of the transmission line losses and voltage profile using TCSC and UPFC are compared in order to demonstrate which FACTS device can produce better results. The IEEE 14 bus system is used in this study to validate the findings.