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Unlocking Accurate Power Quality Analysis Through Optimal Sampling Rates
This white paper explores the critical role of sampling rate in power quality (PQ) recorders, explaining how higher sampling frequencies enable more precise waveform capture, detection of transients, and analysis of harmonics. It details the technical background of analog-to-digital conversion, the impact of sampling rates on data fidelity, and highlights the capabilities of PMI’s Revolution recorder, which achieves microsecond-level resolution for advanced PQ investigations. You’ll see how samples-per-cycle relates to Nyquist limits, why higher rates sharpen harmonic resolution and RMS precision, and how oscillatory transients, narrow notches, and interharmonics can disappear at low rates. The paper also notes that PMI recorders (Revolution and Guardian) sample at 256 samples/cycle or greater, with Revolution’s high-speed mode decimated for standard processing—balancing fidelity and storage.
Key topics include:
- Signals Sampled Over Time
- The Sample Rate
- Waveform Data
- PMI's Revolution Power Quality Recorder
Why utilities should care:
High sampling rates in PQ recorders enable detection of subtle waveform anomalies, accurate harmonic analysis, and transient capture, supporting thorough power quality investigations and informed decision-making for system reliability and compliance. In practice, choosing the right rate is operational, not academic: too low masks switching notches, capacitor restrikes, and fast front events; too high wastes storage and shortens capture windows. The paper provides actionable guidance on setting samples-per-cycle, pre/post-trigger windows, and event criteria so engineers can see conditions leading into a fault, verify protection coordination, and separate upstream system effects from customer equipment. Standardizing on 256 samples/cycle across Guardians and Eagles creates comparable fleets of data, while deploying a Revolution on problem feeders captures microsecond-class transients and interharmonics for root-cause evidence. The result is faster triage, fewer repeat truck rolls, clearer DER interconnection reviews, and defensible reports for regulators and customers—turning elusive “mystery” events into documented, fixable problems and improving planning decisions without over-instrumenting the entire system.
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