Power quality 9810 series - User manual
205 7EN05-0390-08
K-factor
K-factor relates the heating effect of a distorted current in a transformer to a sinusoidal current
with the same RMS magnitude — it describes a transformer’s ability to serve non-linear loads
without exceeding rated temperature rise limits.
The K-factor is equal to the sum of the squares of the harmonic currents multiplied by the squares
of the harmonic order. The meter uses the following equation to calculate K-factor:
Where K is the K-factor, h is the harmonic order and Ih is the true RMS current of harmonic order
h.
Harmonic content calculations
Harmonic content (H
C
) is equal to the RMS value of all the non-fundamental harmonic
components in one phase of the power system.
The meter uses the following equation to calculate H
C
:
THD% calculations
THD% is a quick measure of the total distortion present in a waveform and is the ratio of harmonic
content (H
C
) to the fundamental harmonic (H
1
).
By default, the meter uses the following equation to calculate THD%:
thd and TDD
Your meter can be configured to provide thd (total harmonic distortion using the total RMS value
for the content rather than the fundamental content) and TDD (total demand distortion, the
harmonic current distortion against the maximum demand of the electrical system).
thd = H
C
/ RMS *100%
TDD = H
C
/ Demand
Max
*100%
For more information on the Harmonics Measurement module, see ION Reference, available on
www.usa.siemens.com/pds.
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