Deregulated power systems suffer from congestion management problems. Also they cannot fully utilize transmission lines due to excessive power loss that it could cause. FACTS devices such as thyristor-controlled series compensators (TCSC) can, by controlling the power flow in the network, help reducing the flows in heavily loaded lines. Also they can minimize the power loss of the systems. However, because of the considerable cost of FACTS devices, it is important to minimize their number and obtain their optimal locations in the system. This book presents an approach to find the optimal location of thyristor-Controlled series compensators in a power system to improve the loadability of its lines and minimize its total loss. Also the proposed approach aims to find the optimal number of devices and their optimal compensation levels by using a genetic algorithm taking into consideration the thermal and voltage limits. Examination of the proposed approach is carried out on a several IEEE systems.