In recent years, power demands around the world and particularly in North America increased rapidly due to increase in customers demand, while the development in transmission system is rather slow. This stresses the present transmission system and voltage stability becomes an important issue in this regard. Pattern recognition in conjunction with voltage stability analysis could be an effective tool to solve this problem In this thesis, a methodology to detect the voltage stability ahead of time is presented. This gives the operators a chance to take remedial actions and possibility to...