Adaptive distance relaying scheme in presence of UPFC using WAMS

This paper analyses the impact of unified power flow controller (UPFC) on performance of distance relaying scheme and proposes a new adaptive relaying technique for mitigating the undesirable effects of overreach/underreach shown by the conventional distance relays. The proposed scheme computes on-line control parameters of the UPFC based on synchronized phasor measurements from Phasor Measurement Units (PMU) installed at line terminals. Trip boundaries are generated for the distance relay considering the effects of control parameters of UPFC, fault resistance and system loading condition. Moreover, for deciding the trip boundaries for a given Single Line to Ground (SLG) fault, the information on self protection mode of UPFC (bypass mode), has also been utilized. A generalized regression neural network has been used to identify the trip boundaries of the distance relay. The simulation results show the ability of the generalized regression neural network to identify the trip boundaries inspite of dynamic changes in the control parameters of the UPFC.