Frequency measuring and monitoring apparatus, methods and systems

摘要

Waveform frequency measuring apparatus and methods utilizing zero-crossing triggered analog-to-digital conversion apparatus combined with Discrete Fourier Transform (DFT) digital computing apparatus accomplish measurement of waveform fundamental frequency using hitherto disadvantageous leakage of the Discrete Fourier Transform. In an example, the frequency measuring apparatus and methods are used in an alternating current (AC) electrical power system for measuring and monitoring frequency deviation DELTA f from the nominal system frequency f and actuating protective relaying when the frequency deviation is excessive.