Recognition of Fault Section During Power Swing in the Presence of TCSC Environment

Power swing causes oscillations of active and reactive powers. Modulation of electrical signals within duration of power swing generates unnecessary trips of relays and severely affects protection techniques. Power swing blocking prevents relay operation within the period of power swing, which freezes detection algorithms. Further, employment of TCSC in transmission networks within the period of power swing increases protection complexities due to voltage and current inversion, nonlinear behavior of MOV, and sub-synchronous oscillations. Local-end measurements-based conventional backup protection schemes are unable to identify faults properly during power swing. In this paper, a synchronized phasor measurement-based wide-area backup protection approach is proposed for fault section recognition in a TCSC installed transmission line within the period of power swing. Fault section recognition consists of the fault bus recognition and fault direction estimation approaches. Here, the bus closest to fault is recognized using Clark’s transformation of voltage signal-based approach and direction of fault is determined by an integrated approach. The approach-1 for fault direction is based on phase difference between superimposed negative sequence voltage and superimposed negative sequence current, and approach-2 is based on phase difference between superimposed positive sequence voltage and superimposed positive sequence current. The proposed approach is tested for different symmetrical and unsymmetrical fault cases that occurred in different sections of transmission lines. The proposed approach is validated on a WSCC 9-bus, 400 kV, 50 Hz system and simulated and tested using EMTDC/PSCAD software.