This paper proposes the use of series FACTS devices to relieve congestion and enhance the security in restructured power system. Harmony search algorithm as a novel heuristic algorithm is employed for optimal locating and sizing of series FACTS devices. In order to reduce the solution space and to pinpoint the lines which are more suitable for FACTS device placement line outage sensitivity factors is employed. Two different objective functions are considered in the optimization problem, the first one is the total congestion cost and the other is total generation cost. To validate the effectiveness of the proposed method and show its efficiency, the simulations are carried out on IEEE 14-bus test system. The results of the proposed method are compared with those obtained by particle swarm optimization and with those obtained by congestion rent contribution method.