A method and device for measuring electrical grid data in the presence of noise is disclosed. Noisy frequency data is received from the grid. The noisy data is filtered above a predetermined frequency. The filtered data is differentiated using band-limited differentiator. The data may be filtered and differentiated simultaneously by the band-limited differentiator.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with Government support under Contract DE-AC0576RLO1830 awarded by the U.S. Department of Energy. The Government has certain rights in the invention.