MODAL KALMAN FILTERING BASED IMPEDANCE RELAYING

A new algorithm is presented for computer distance relaying that is based on Modal Kalman Filtering (MKF) to estimate fundamental phasors. MKF exploits all the measurement information available from a three phase line, and is founded on enhanced models of the electromagnetic transient noise. To support the modeling of noise for different faults, a study over non trivial electrical networks with accurate electromagnetic transients modeling is developed for 400 kV transmission lines. MKF fits the behavior of the different modal noise for the Clarke phasors , but is invariant for each type of fault, assuring robustness and minimum error variance. To compute distance, first Clarke alpha-beta-phasors are transformed to +/- symmetrical components, and next a well known expression is used to compute the positive impedance. Statistical analysis is presented to assess observation time versus estimation accuracy for the different types of line faults.