© 2008 Siemens Energy & Automation, Inc. All Rights Reserved.
PMCM-9340D-0208 ACCESS 9340 and 9360 Meters
2/2008 Chapter 4—Metering Capabilities
EN–57
Power Analysis Values
The meter provides a number of power analysis values that can be
used to detect power quality problems, diagnose wiring problems,
and more. Table 4–6 on page 58 summarizes the power analysis
values.
• THD. Total Harmonic Distortion (THD) is a quick measure of the
total distortion present in a waveform and is the ratio of harmonic
content to the fundamental. It provides a general indication of the
“quality” of a waveform. THD is calculated for both voltage and
current. The meter uses the following equation to calculate THD
where H is the harmonic distortion:
• thd. An alternate method for calculating Total Harmonic
Distortion, used widely in Europe. It considers the total harmonic
current and the total rms content rather than fundamental content
in the calculation. The meter calculates thd for both voltage and
current. The meter uses the following equation to calculate thd
where H is the harmonic distortion:
• Displacement Power Factor. Power factor (PF) represents the
degree to which voltage and current coming into a load are out of
phase. Displacement power factor is based on the angle between
the fundamental components of current and voltage.
• Harmonic Values. Harmonics can reduce the capacity of the
power system. The meter determines the individual per-phase
harmonic magnitudes and angles through the:
— 31st harmonic (ACCESS 9340) or
— 63rd harmonic (ACCESS 9360)
for all currents and voltages. The harmonic magnitudes can be
formatted as either a percentage of the fundamental (default), a
percentage of the rms value, or the actual rms value. Refer to
++
H
2
2
H
3
2
H
4
2
+
x
100%
THD =
H
1
++
H
2
2
H
3
2
H
4
2
Total rms
+
x
100%
thd =
To Next Page
Loading...
Need help?
General
