This paper presents detailed fast control characteristics and continuous compensation capability. Flexible AC Transmission System (FACTS) devices have been researched and adopted in power engineering area. There are so many advantages of FACTS device; it can increase dynamic stability, loading capability of lines, improve power quality and system security. It can also increase utilization of lowest cost generation. The key role of FACTS device is to control the power flow actively and effectively. In other words, it can transfer power flow from one line to another within its capability. This paper presents detailed improving power system quality using advanced flexible AC transmission systems (FACTS) controllers, namely, Advanced Thyristor Controlled Series Capacitors (ATCSCs), Advanced Thyristor Controlled Series Reactor (ATCSR), Advanced Static Var Compensator (ASVC) and Advanced Static Var System (ASVS). This paper focuses on the operation of the FACTS device under generator fault that may cause any other transmission lines to be overflowed. The proposed algorithm in this paper is tested on the IEEE 30 bus system.