An Amplitude-Based Threshold Design Process for Reliable RMS-Energy Oscillation Detectors

Oscillation detection is one of the key reliability-enhancing capabilities enabled by phasor measurement unit (PMU) technology. Several grid operators have deployed commercial platforms that implement oscillation detection by monitoring the RMS-energy of measured signals. Oscillations are detected when the signal's energy crosses a predetermined threshold. The current process of setting these thresholds requires the analysis of at least three months of historical data, which is time consuming and expensive. The thresholding process seeks to avoid false alarms, but it does not evaluate the likelihood that a given oscillation amplitude will trigger detection. As a result, thresholds often require re-tuning to avoid nuisance alarms. This paper proposes a method for designing RMS-energy thresholds that directly integrates oscillation amplitudes selected by the practitioner. The method improves upon previously published work by providing the practitioner with 1) guidance on the range of amplitudes that will lead to a successful design, and 2) a complete summary of the threshold's expected performance. The method is explained and tested using field-measured PMU data to demonstrate its practical viability.