Variance Index of Three Phase Instantaneous Power based Fault during Power Swing

Distance relays are intended to operate reliably and secured manner, and are rigorously complied with to eschew mal-operation during stressed condition. To eschew these conditions, power swing blocking functions (PSB) is included in the distance relay design. But, any kind of fault is commencing during swing, the PSB function should unblock it and provides trip signal to the circuit breakers (CB). Unsymmetrical fault cases were facilely unblocked, except in the case of symmetrical fault during power swing condition is a difficult task for relay unblocking due to balanced phenomenon. Variance indexes of three phase instantaneous power signal (VITPIP) predicated symmetrical fault detection during power swing is presented in this paper. The method utilizes quantified three-phase voltage and current signals from relay end. Extraction of high frequency components of three-phase instantaneous power signals utilizing DWT. Subsequently, variance index is estimated for the details coefficients of power signals avails to discriminate the symmetrical fault from swing event. To validate the accuracy of the proposed technique, a 400 kV, 50 Hz single machine illimitable bus system is considered and simulated in the MATLAB / SIMULINK platform. Different critical cases such as fault inception time, slip frequency, fault resistance and fault location were considered for the simulation. The results, it illustrates that the proposed method is more efficient.