In modern power system many protection equipment are connected in complex network. They are interconnected with each other. The rising demand of power and difficulties of constructing a newly transmission network causes the power system to be complex and stressed. Due to the stress in the power system there is a chance of losing the stability following to the fault. To reduce this problem use Flexible AC Transmission System (FACTS) devices which are uses power electronics components to maintain controllability and capability of electrical power system. After introducing the facts technology, power flow along the transmission lines becomes more flexible and controllable.