Methods of Forming Orthogonal Components of Input Signals for Relay Protection

The existing frequency digital filters for allocation of the fundamental frequency of a sine signal are considered and their advantages and disadvantages are noted. Preference is given to the combined digital filter. The existing methods of determining the orthogonal components of a sine signal are analyzed and their disadvantages are pointed out. It is concluded that most of the existing methods for determining orthogonal components are sensitive to the fundamental frequency deviation of the sine signal. This is due to the fact that the deviation of the frequency alters the angle of one sample. The method for solving this problem has been proposed. The essence of the method is the dynamic recalculation of the angle of one sample depending on the calculated frequency. The mathematical model for research of ways of formation of orthogonal components is presented. The model includes transient generator taking into account the aperiodic component, combined digital filter and the methods of formation of orthogonal components under study. The method of transient phenomena formation that takes into account the aperiodic component is described. Coefficients of combined digital filter for sampling frequency of 1200 Hz are given. One of the implementations of the proposed method of formation of orthogonal components in the programming language MatLab is presented. One of the more popular methods and the proposed method acted as the formers of orthogonal components under study. The final part of the article presents the results of the research, as well as their analysis.

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