A New Method for Fast Removal of Decaying Offset in Relaying Input Current

Abstract

Phasor estimation is still the primary method of high-speed measurements used in electrical power system protection and control. Widely applied filter algorithms are based on the discrete Fourier transform (DFT), which can easily erase harmonics. However, the voltage and current waveforms that accompany short circuits in the network contain both harmonic components and decaying DC (DDC) components. Various methods of reducing the effect of the decaying aperiodic component on the accuracy of determining the amplitude and phase of the current’s fundamental component have been proposed for decades. Judging from recent publications, the issue is still relevant. The presented method proposes to change the known paradigm by including a modified signal model in the transition state of the algorithm with an expanding measurement window. The measured signal is shown to be represented by the sum of the orthogonal components of the corresponding harmonics and the mapping of the DDC components. The simulation studies conducted show the properties of the presented method.