An algorithm for frequency relaying based on the Newton-Raphson method

This paper presents a new digital algorithm for real-time estimation of the frequency at a power system bus. The algorithm is based on the Newton-Raphson method, which is very commonly used in load flow studies, and uses digitized samples of voltage at a relay location. The mathematical development of the algorithm is presented and the effects of key parameters affecting the performance of the algorithm are discussed. The algorithm showed high measurement accuracy over a wide range of frequency changes, even in the case of harmonic-distorted input signal processing. The presented work is part of a project concerning the development of numerical algorithms in frequency relaying. The algorithm presented could also be used for the identification and measurement of power system harmonics. Results of numerical tests are presented to demonstrate the properties of the proposed algorithm. © 1994.