Rate of change of frequency measurement

The measurement of amplitude, frequency, rate-of-change of frequency, and phase of an alternating waveform is the purpose of the Phasor Measurement Unit, PMU. Performance requirements, specified by standard, are tested with constant values of each of these parameters, using a synthetic waveform with values that are precisely known. However, device performance requirements are not defined during transitions from one set of values to another. We investigated measuring across a transition. Our investigation revealed something interesting about ROCOF, the rate of change of frequency. We conclude that until power system noise is better understood, the attempt to measure real-world ROCOF during a short PMU measurement window should be abandoned, but measurements during calibration transitions might still be possible and need not be excluded from the standard.