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Mains Frequency Fluctuation Metering

Sibanic, Sofia (2013) Mains Frequency Fluctuation Metering. Other thesis, Murdoch University.

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Detecting the frequency of the mains supply is a crucial component of maintaining the grid frequency at its nominal level. Most frequency counters enable the user to monitor frequencies but monitoring frequency variations at a high resolution is often expensive. Electronic systems that measure frequency also have to generate a local time base to calculate the frequency upon. All time bases suffer from the effect of frequency jitter, which makes the timing source deviate from the nominal second by a quantified amount. Modern systems have improved drastically and have relatively insignificant jitter for most timing applications, but high-precision applications require a quantification of this source of timing error.

The purpose of this thesis is to document the background, implementation, testing, results and identified future improvements for a frequency meter that can record minor fluctuations of the grid frequency. By achieving this objective, the grid supply and demand data can be logged and used for several applications, such as network forecasting or maintaining nominal grid frequency.

An extensive research period was required to determine key design facets pertaining to the frequency meter. Key identified tasks included choosing a timing source, finding a suitable software development platform and associated hardware, developing a graphical software implementation that displays real-time frequency fluctuations, contingency alarming for nominal frequency deviation events, communications design between the frequency meter and the PC, quantifying clock precision and evaluating the performance of the final frequency meter.

A GPS time source was chosen to provide an accurate source of 1 second pulses. An Arduino Due microcontroller used a KX-7 quartz crystal oscillator to maintain its time base and the accuracy of the KX-7’s time base was analysed against the Trimble Copernicus II and GlobalSat EM406-A GPS receivers’ time base. When analysed relative to the GPS receivers’ accurate time base, the KX-7 maintained a low time base variation, well within it’s data sheet specifications.

The Arduino Due microcontroller was programmed and provided relevant frequency data to a LabVIEW PC terminal, which allowed frequency visualisation, data storage, grid frequency contingency detection, recovery time logging, GPS initialisation data and cross-platform communication protocols.

Frequency data was logged on the frequency meter and was able to provide a microHertz resolution. The primary limitation of the design was low-level noise on the mains supply line as this affected the designed electronics when logging frequency measurements below the milliHertz range. Multiple recommendations for future work have been identified and included in this report.

Item Type: Thesis (Other)
Murdoch Affiliation(s): School of Engineering and Information Technology
Notes: ENG460
Supervisor(s): Lee, Gareth
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