An adaptive secure-dependable wide-area backup protection scheme for transmission lines using Multi-Phasor Measurement Units

This paper proposes an adaptive secure-dependable wide-area backup protection scheme for protection of transmission lines using Multi-phasor Measurement Units (MPMU). MPMU is an extended version of Phasor Measurement Unit (PMU). MPMU is an intelligent electronic device which estimates the synchronized predominant harmonic phasors (100Hz and 150Hz) besides the fundamental phasors (50Hz) of three phase voltages and currents with high precision. In this paper, the measured harmonic phasors (measured at MPMU) of the three phase currents are employed to detect faults and classify the faulted phase for enhancing the dependability attribute of the wide-area backup protection (WABP) of transmission system. The proposed methodology also recognizes the other transient events such as power swing, load encroachment and unbalanced load for improving the security attribute of WABP system. The performance of the proposed methodology for secure-dependable WABP is validated on a two generator power system. The proposed methodology is immune to variation in fault resistance, fault inception angle and fault distance and can achieve the security-dependability balance during faults and transient events (other than faults) to assist system protection center (SPC) in taking appropriate decision to any catastrophic situation in case of failure in main protection system.