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Fourier analysis is performed on four full waveform cycles providing a harmonic
spectrum resolution of 1/4 of the fundamental frequency, so harmonic magnitudes
are not falsified by adjacent frequencies. Due to simultaneous sampling of voltage
and current waveforms on each phase, harmonic voltages and currents are evaluated
with their respective phase angles providing calculations of harmonic powers and
power factors. Using certain techniques, those can help the user determine the
direction of harmonic power flow and to assess harmonic impedances at different
locations on the network.
4.5.2 Harmonic Parameters
Harmonic quantities for which the PM295 provides on-board measurements include:
• phase voltage and current total harmonic distortions (real-time and average)
• phase K-Factors (real-time and average)
• real-time phase voltage and current harmonics up to 40th
• real-time phase harmonic voltages and currents for odd harmonics up to 39th
• real-time harmonic total powers (active and reactive) for odd harmonics up to
39th
• real-time harmonic power factors for odd harmonics up to 39th.
Total harmonic distortions (THD) and K-Factors are calculated over the first 40
harmonics.
NOTES
1. In 4-wire connections using either 4Ln3 or 4LL3 wiring mode, harmonic
voltages will represent line-to-neutral voltages. In a 3-wire direct connection,
harmonic voltages will represent line-to-neutral voltages that arise on the
Powermeter's input transformers. In a 3-wire open delta connection, harmonic
voltages will comprise only L12 and L23 line-to-line voltages.
2. Harmonic measurements for phase currents are provided only for those that
are present on the instrument' s inputs.
3. Total harmonic powers and power factors will be calculated correctly in all
wiring configurations except of a 3-wire direct connection with two currents. If
the third current is also supplied, these calculations will be provided correctly
too.
For harmonic calculations, each subsequent measurement provides processing of one
input, so that total three-phase harmonic measurements for 6 inputs might require
more than one second.
Operation Techniques
65
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