On proper control in transmission network, overloading can be eliminated or reduced by power sharing in interconnected transmission system, by introducing FACTS device in power system network. To improve power system performance, TCSC device from FACTS family has high potential in applications including transient stability improvement, reduction in power loss, control over real power flow, capability of transfer of power enhancement in transmission system and mitigating sub synchronous resonance etc. This paper present TCSC-a facts device optimal size and proper location on transmission line system because of high cost and attain its benefits of TCSC in transmission system. This paper also describe, the discussion, work performed by researchers in this field of finding optimal location, size of TCSC-its application on power system stability improvement and control strategies. © IJSTR 2019.