Behaviour of Fourier, cosine and sine filtering algorithms for distance protection, under severe saturation of the current magnetic transformer

The aim of the present work is to analyse the behaviour of the Fourier, sine and cosine digital filtering algorithms in impedance calculation, considering a distorted current signal due to severe saturation of the CT. To this aim we consider the effect caused by data window length variation, and the analogue anti-aliasing filter on the algorithm output. The current signals considered in this work have been obtained from a power test in which an intentional short circuit was produced, and the primary and secondary currents of the CT submitted to test were recorded