AN ALGORITHM FOR FREQUENCY RELAYING BASED ON THE NEWTON-RAPHSON METHOD

This paper presents a new digital algorithm for real-time estimation o f the frequency at a power system bus. The algorithm is based on the N ewton-Raphson method, which is very commonly used in load flow studies , and uses digitized samples of voltage at a relay location. The mathe matical development of the algorithm is presented and the effects of k ey 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 de velopment of numerical algorithms in frequency relaying. The algorithm presented could also be used for the identification and measurement o f power system harmonics. Results of numerical tests are presented to demonstrate the properties of the proposed algorithm.