Fluke 1744 User Manual
Power Quality Logger
Methods of Logging
35
Calculation of THD in Measuring Function P
THD – Measuring Function P
Function P does not measure harmonic values.
Voltages:
1
2
1
2
V
V
V
THDV
RMS
−
=
V
RMS
: RMS value of total signal
V
1
: RMS value of the fundamental
Currents:
1
2
1
2
I
I
I
THDI
RMS
−
=
I
RMS
: RMS value of the total signal.
I
1
: RMS value of the fundamental.
Note
THDI for currents < 5% of IE (measuring range) can have additional
uncertainties, or can be suppressed.
uncertainties, or can be suppressed.
Harmonics up to 50th order are taken into account.
Flicker
Flicker is the visual impression of unsteadiness in a light source whose
luminance or spectral distribution changes over time. Flicker is logged in
accordance with the IEC 61000-4-15 standard. The short-term (st) flicker Pst
luminance or spectral distribution changes over time. Flicker is logged in
accordance with the IEC 61000-4-15 standard. The short-term (st) flicker Pst
t
is logged over a default standard interval of 10 minutes, and is used to
calculate the long-term (lt) flicker Plt (by taking the sliding average of 12
short-term values). The interval value can be changed as needed in PQ Log.
calculate the long-term (lt) flicker Plt (by taking the sliding average of 12
short-term values). The interval value can be changed as needed in PQ Log.