A Fault Detection and Classification Scheme for Unified Power Flow Controller Compensated Transmission Lines Connecting Wind Farms

Abstract

In recent years, there is an increasing trend of integrating large capacity offshore wind farms into power grids through UPFC compensated TLs for accommodating large flow of power. The nonlinear fluctuations of output power due to unpredictable variation of wind speed and the different operating modes of the UPFC greatly affect the performance of the conventional distance relaying-based TL protection scheme. This article investigates the impact of such TLs on distance relay performance and proposes a two criteria-based new fault detection and classification scheme. The method utilizes the sign of the change in the magnitude of positive-sequence current at both ends of the line for fault detection and the transient monitor index derived from the locally measured three-phase current for fault classification. The performance of the proposed scheme is evaluated on different fault and nonfault transients generated on two standard test systems through EMTDC/PSCAD during different operating modes of UPFC and at different wind speed. The performance of the proposed scheme is further validated through dSPACE DS 1103-based real-time digital simulation platform. Finally, the comparative assessment results with some important existing methods justify the effectiveness of the proposed method.