Dealing with front-end white noise on differentiated measurements such as frequency and ROCOF in power systems

Roscoe, Andrew J. and Blair, Steven M. and Dickerson, William and Rietveld, Gert (2018) Dealing with front-end white noise on differentiated measurements such as frequency and ROCOF in power systems. IEEE Transactions on Instrumentation and Measurement. ISSN 0018-9456 (https://doi.org/10.1109/TIM.2018.2822438)

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Abstract

This paper describes the way that white noise (including quantised input section sampling) imparts errors onto frequency and rate-of-change-of-frequency (ROCOF) measurements. The main paper focus concerns the use of filtered heterodyned (i.e. Fourier) analyses for single-phase and 3-phase systems, and the filtered Clarke transform for 3-phase systems. The rules and equations governing the effect of white noise on frequency and ROCOF are formulated for these techniques, explaining the subtle effects of aliasing, splitting signals and noise into their positive and negative frequency components, and the correlation or de-correlation of noise. It is shown that - as expected - for 3-phase AC measurements, averaging 3 single-phase Fourier measurements produces the same performance against noise as using a method based on Clarke’s transform, if identical filtering is used. Furthermore, by understanding the theory behind the frequency and ROCOF measurement processes, it is shown that to achieve the lowest RMS errors, in the presence of front-end white noise (alone, ignoring other dynamic signal and power quality aspects), a filter which provides ~40 dB/decade attenuation (i.e. a 2-boxcar cascade) is recommended for a frequency measurement, but a filter which rolls off at ~60 dB/decade (i.e. a 3-boxcar cascade) is recommended for a ROCOF measurement.

  • Item type:Article
    ID code:63576
    Dates:
    Date
    Event
    25 April 2018
    Published
    25 April 2018
    Published Online
    15 March 2018
    Accepted
    Notes:(c) 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.
    Subjects:Technology > Electrical engineering. Electronics Nuclear engineering
    Department:Faculty of Engineering > Electronic and Electrical Engineering
    Depositing user: Pure Administrator
    Date deposited:03 Apr 2018 14:23
    Last modified:13 Apr 2024 05:17
    Related URLs:
    URI:https://strathprints.strath.ac.uk/id/eprint/63576
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