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Here is a practical situation: We are measuring harmonics with a Class-A PQ device. At certain times we have the fundamental values of current higher than the true RMS values. I would like to know if such phenomena can happen and in what situation.

JRE
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Hari
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    if you're measuring peak values, obviously they can exceed RMS values for the same quantity. –  Jan 10 '22 at 14:16
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    For sine signal the peaks are always higher than RMS... – Eugene Sh. Jan 10 '22 at 15:04
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    The RMS is effectively a measurement of power. Power is non-negative. The total power of a signal will always be the sum of its components, and each component will be no larger than the total. If a component measures more than the total, this indicates a problem with the measurement, not new physics or new maths. – Neil_UK Jan 10 '22 at 15:09
  • Are you sure that the Class-A PQ is "well-calibrated" device ? – Antonio51 Jan 10 '22 at 16:53

1 Answers1

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$$\text{RMS of a signal} = \sqrt{A^2 + B^2+C^2 + D^2+...}$$

So, no matter what value you ascribe to B, C and D harmonic amplitudes, the RMS of a harmonically distorted signal can never be less than the RMS of the A quantity (or B quantity etc.). See this wiki article for the RMS of waveform combinations: -

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Andy aka
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