A new digital transformation for harmonics and DC offset removal for the distance fault locator algorithm

Abstract

This paper presents a new application of Park's transformations to identifying the positive sequence of the fundamental components of the three-phase voltage or current signals needed for fault locator algorithm. The problem is solved in two steps; in the first, we identify and filter the DC offset as well as harmonics that contaminated the signals using Park's transformation. In the second step, the digital residuals, which are the difference between the original signal and the harmonics plus the DC offset, are the digital samples of the positive sequence component of the fundamental waveforms. These samples are then used to estimate digitally the positive sequence of the fundamental components using the least error squares estimation algorithm. It is obvious to state here if the fundamental components are balanced, the estimated positive sequence components equals the fundamental components. The paper starts by reviewing the new transformation matrices, then the proposed steps beyond the algorithm are explained, and finally results for simulated examples and for actual recorded data are reported.