Comparison of Wavelet Transform and Fourier Transform based methods of Phasor Estimation for Numerical Relaying

Estimation of fundamental frequency component of current and / or voltage signals is essential for relaying decision in most of the numerical algorithms used for the protection of power system components. Modern numerical relays generally use discrete Fourier transform for extracting the fundamental component from the post fault signals consisting of fundamental as well as non-fundamental frequency signals. With the advent of wavelet analysis, many researchers used wavelet analysis for the phasor estimation with the claims of better performance. The paper compares the performance of discrete wavelet transform method with discrete Fourier transform method for phasor estimation, considering the effect of decaying dc offset. MATLAB software was used for programming and simulation. Keywords-Decaying dc offset, fundamental frequency component, phasor estimation, numerical relaying, wavelet transform