Flexible Alternating Current Transmission Systems (FACTS) devices can provide strategic benefits for transmission system management through better utilization of existing transmission facilities, increasing system capacity and reliability, enhancing system stabilities, as well as enabling ecological benefits. In addition, FACTS devices can be used to minimize transmission system power loss, and power flow control flexibility and rapidity. Though FACTS controllers offer many advantages, their installation cost is very high. Hence the optimal placement and the optimal parameter settings of these devices in the power system are of important issues. This paper presents the optimal location and the optimal parameter setting of TCSC considering the active power losses minimization in the power network based on one of the newest Evolutionary Optimization Techniques, namely Differential Evolution (DE), also compare it is performances with Genetic Algorithm (GA). For the validation and comparison purposes of the proposed techniques, simulations are carried out on several power systems, a three-bus power system, a five-bus power system, and an IEEE-14 bus power system. The results, we have obtained, shows that DE is an easy to use, robust, fast and powerful optimization technique compared with genetic algorithm (GA). The results are presented in the paper together with appropriate discussion.