A Time Varying Filter-EMD Based Intelligent Technique for Protecting UPFC Installed Transmission Line

The conventional distance relays exhibit limited performance while used for the protection of unified power flow controller (UPFC) compensated transmission lines (TLs) due to rapid changes of voltage and current signals during various operational modes of UPFC. This paper investigates the impact of the different operating modes of UPFC and propose an improved protection algorithm for the relay. The sign information of one-cycle differences of $\alpha$-aerial currents at line ends are used to detect an internal fault. Then, the features extracted from time-varying filtering-empirical mode decomposition (TVF-EMD) are used in the decision tree (DT) classifier for fault type identification. The proposed protection algorithm is verified by creating various fault/non-fault cases in a 220 kV two-bus system modelled in MATLAB/Simulink. The fast response and high accuracy clearly provide adequate ground for the performance of the proposed protection technique for UPFC installed TL.