On the application of /spl alpha//spl beta/-transformation for power systems frequency relaying

This paper presents a new and very accurate algorithm for power system frequency measurement. The proposed algorithm is based on /spl alpha//spl beta/-transformation of the three phase voltages or current waveforms in the relay location, where digital samples are available for the three phase waveforms. Having obtained the digital samples of one of the components, /spl alpha/-/spl beta/ components, the finite divided difference formulae are used to calculate the parameters of one of these components; the magnitude, the frequency and phase angle. The necessary formulae are derived within the text and effects of imbalance and harmonics contamination on the waveforms are discussed within the text.