A Future Standard for Reactive Power Measurement

Reactive power is defined for sinusoidal voltage and current. Several different ways to measure the quantity have been developed, and while they all give the same result for sinusoidal voltages and currents, the results are not the same when the inputs are distorted. Work was done with distorted test signals to explore these - sometimes large - differences, and a report summarizing the findings was published by the US National Institute of Standards and Technology (NIST) in 2011. We show in this paper that the differences are smaller, but still not negligible, when the waveforms are less distorted. The differences between the results of the various existing methods are discussed from the viewpoint of measurement theory. The paper argues that it is time to select one measurement method. The relevance to the ongoing revision to IEEE standard 1459 (which defines reactive power for the purposes of measurement) is explored.