This paper investigates operational benefits of integrating thyristor controlled series capacitor (TCSC) in Korean electric power system. Critical challenges of balancing the electricity demand rise and deferred transmission construction due to the public opposition and environmental impact as well as unique topological issues of the power grid, endanger reliability of the system. Installation of flexible ac transmission systems (FACTS) is envisioned to be a low-environmental impact technology that effectively resolve these issues. In particular, this research exploits flow control capability of TCSC and examines the benefits of improving transmission capability and security. It presents a series of studies for identifying the adequate location and size of the TCSC and discusses practical issues and lessons learned through studies.