Simultaneous impact of unified power flow controller and off-shore wind penetration on distance relay characteristics

This study presents an analytical approach for finding the possible impacts of flexible AC transmission system (FACTS) devices such as unified power flow controller (UPFC) and off-shore wind penetration on distance relay characteristics. Generating relay tripping characteristics is one of the challenging issues for transmission line distance relays as the present day transmission systems is subjected to a more stressed environment with respect to power system operation. Moreover, inclusion of FACTS devices such as UPFC in the transmission system seriously impacts the performance of the distance relays as the apparent impedance changes. Furthermore, the reach setting of the relay is significantly affected as the relay end voltage fluctuates continuously when off-shore wind-farms are connected to power transmission systems. Thus, generating tripping characteristics for appropriate operating conditions is a demanding concern and the same has been addressed in the proposed research work. Extensive testing is carried out in generating relay tripping characteristics with possible variations under the operating conditions of UPFC and wind-farm and it is observed that the characteristics are significantly affected for different operating conditions. Furthermore, the performance of the derived relay characteristics is validated on possible transmission line fault events and is found to work effectively.