Digital measurement of symmetrical components for power system protection

Abstract EN

The theory of symmetrical component assumes that the original unsymmetrical system is sinusoidal with fundamental frequency, and is contaminated with no harmonics.

Nowadays, power system networks are subjected to harmonics injection due to the widespread use of power electronic equipments in power systems transmission and control.

In this case, the symmetrical components theory is not applicable, and an accurate method is needed to calculate the symmetrical components.

This paper presents the applications of parameter estimation techniques for measuring the symmetrical components for power system protection.

The least errors square (LES) is the parameter estimation algorithm used to estimate these components from the digitized samples of the unsymmetrical system.

Here, we assume a three phase unsymmetrical system of voltages which is contaminated with harmonics.

The three symmetrical components, namely the positive, negative, and zero sequence components are estimated using the proposed technique.

Effects of sampling rate and data window size, as well as, the frequency drift are examined.

The algorithm is tested using simulated and actual recorded data.

The results obtained are reported in the text which form the basis to our conclusions.