Fault discrimination by power protections during transient disturbances

Abstract

During first dozens of milliseconds from the moment when the fault occurs, the transient components due to the fault can appear in the short circuit currents and voltages. The latter could have a form of either the attenuated oscillating components or the non-periodical components making troubles to be filtered. Then, the highly inconvenient conditions for the fast short-circuit protections can appear due to specifics of the measuring signals disturbances the separation of which is very difficult. Traditionally, the measuring signals disturbances are eliminated using either the Fourier transform (FT) or the Fast Fourier Transform (FFT). The different tool of signal analysis is the wavelet transform (WT). In the paper, referring to an example of typical non-stationary signals, a comparison of the both analysis methods referred to the protective measuring algorithms is carried out. A special attractiveness of the wavelet transform is proven.