Adaptive harmonic estimation technique for reduction the blocking time of transformer for differential protection

This paper presents a new adaptive methodology for 2^nd harmonic estimation of transformer differential protection in order to reduce the blocking time of transformer in inrush condition. The proposed algorithm provides a useful tool for signal estimation in non-sinusoidal power system such as faulty conditions or switching time. This method employs a variable window length algorithm for signal estimation, which is extended through time passing, and uses only post-fault data for signal estimation. Also, conventional Discrete Fourier Transform (DFT) was compared to this method. Moreover, the simulated results presented clearly, the proposed algorithm can accurately estimates the 2^nd harmonic in less time than conventional methods like conventional DFT.