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Have you ever noticed a wave shape like this, but your meter is saying that it only has 2-2.5% THD!? The below wave shape has been normalized to a peak voltage of 1. The actual waveform was in the 69 kV to 161 kV range.
I have not seen this often yet, but a customer wanted to know why his THD reading on one screen said ~7.5%, but the IEEE519 report only showed a THD ~2.5%!
This is due to our ION meters having 2 sets of modules that are calculating harmonics. The Harmonic Measurement Modules which are used to calculate harmonics per IEEE519's recommended calculation for short term and very short-term harmonic measurement periods. The Harmonic Measurement Modules only calculate harmonics to the 50th order. The other module is the Harmonics module in the ION 8650 meters, and the Harmonics module is present in the A, B, and C model! The harmonics modules use a 1 second aggregated value but goes to the 63rd harmonic.
Our ION7400, ION8650, and ION9000 meters have both the Harmonic Measurement modules, and the Harmonics module available. And all three meters support the PME IEEE519-2014 power quality report that comes with the software. The ION7400 is limited to the 40th harmonic, and the 8650A model is the only 8650 model that supports the PME report.
The PME supported IEEE519 report only uses the values from the harmonic measurement modules which provides a THDv value of around 2.5% for the above wave shape. But the PME Vista diagram for this template is looking at the harmonics module output which is looking beyond the 50th harmonic.
In the waveform capture above it was found that the 55th order harmonic was the greatest at roughly 3% on each phase.
Please contact the US Power & Grid Sales team for more information.
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