Impact of UPFC on distance relay: A case study

In the power transmission system FACT controller is incorporated in the transmission line in order to increase power transfer capability as well as reactive power control. The FACT devices which combine the feature of shunt fact devices and series fact devices are considered i.e. UPFC (Unified power flow controller) which address the issue of adaptive protection of a transmission line where this device is located at the different position of transmission line like middle of the transmission line, sending end and receiving end of transmission line. Design and simulating the UPFC incorporated in transmission line is done in PSCAD/ EMTDC software. The impact of UPFC on the distance relay is described by impedance trajectory, disturbance in voltage and current and apparent impedance is carried out in the presence of UPFC for different fault calculation.