Advantages in using Kalman phasor estimation in numerical differential protective relaying compared to the Fourier estimation method

This paper demonstrates the results obtained from detailed studies of Kalman phasor estimation used in numericaldifferential protective relaying of a power transformer. The accuracy and expeditiousness of a current estimate in thenumerical differential protection is critical for correct and not unnecessary activation of the breakers by the protecting relay, and the objective of the study was to utilize the capability of Kalman phasor estimation in a signal model representing the expected current signal from the current transformers of the power transformer. The used signal model included the fundamental frequency, an exponentially decaying current, the 2nd and the 5th harmonic to the fundamental frequency