Today's power system continues to expand exponentially due to extensive automated need for both domestic and industrial needs. The expansion of power transmission networks is limited due to environmental right of way and economic reasons. The ever growing demand of power system network has resulted in rotor angle oscillations and voltage instability. It is precisely due to the inability to generate the required reactive power and real power control that propounds the cause of voltage collapse and rotor oscillations. Therefore it is time to focus on the use of the shunt reactive compensation devices to alleviate this issue of voltage stability and series reactive compensation devices to improve the rotor angle stability. Flexible AC Transmission Systems (FACTS), which have recently been developed in power electronics, can make it easier to control the flow of power, boost power transfer capabilities, lower the cost of generating, improve security, and enhance the stability of power systems. The growth of large interconnected power systems demands faster response to maintain stability. Therefore it is also necessary to develop computationally intelligent controllers based FACTS devices for faster and more accurate control action. The objective of this paper is to analyses stability enhancements in power system networks by FACTS devices like GCSC and TSSC. In this work small signal stability and transient stability analysis of the above FACTS devices are investigated. From the analysis it is proved that TSSC is the best FACTS device for transient stability enhancements.