Study on factors affecting distance protection scheme of UPFC compensated transmission lines

The advancements of technology in present time have led a steep rise in power consumption and its demand. To meet the everlasting growth of power demand, electric utilities are opting for capacity expansions and modernization of existing networks. Incorporation of flexible ac transmission systems (FACTS) devices into existing system is one of preferred choices of modernization because this step enhances the transmission line capacity of the existing network thus, preventing the utilities to go for capacity expansions. Additionally, FACTS devices increase the power quality and reliability of the system. Unified power flow controller (UPFC) is most preferred FACTS device due to its versatility in regulating voltage and power transfer. However, the incorporation of FACTS devices in the transmission system may hamper the protection system. In several studies, it is found that FACTS devices affect the coordination of protective relays resulting in either underreaching or overreaching of the relays. Thus, this paper presents study of different factors which affect the distance protection scheme of UPFC employed lines. In this event, the considered factors are installation point of UPFC, operating modes of UPFC, location of fault, different fault resistances, different fault inception angles, different type of faults and external faults. MATLAB environment is chosen as the simulation platform for all simulation studies.