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2857-570/024-001
Functions
34
Product manual | Version: 2.0.0
3-Phase Power Measurement Module, 1 A
metering.
For each phase, active, reactive and apparent power can be determined individually via
the Interface Configuration Software or parameters 27, 28 and 29.
Determining the Frequency
The phase frequencies are calculated using zero crossing detection of the sampled sig-
nals for each phase. The min. and max. frequencies are determined over a configurable
time period (scd or parameters 24, 25, and 29).
Harmonic Analysis
Note
Meaning of "upper harmonic"
“First harmonic” refers to the vibration at the fundamental frequency (fundamental compo-
nent), and “first upper harmonic” refers the vibration at twice the fundamental frequency.
Therefore, in general, the nth harmonic corresponds to the (n−1)th upper harmonic.
The product calculates the frequency spectrum for the periodic input signals and ana-
lyzes the fundamental component and the first to the 40th upper harmonics for each
phase, i.e. the first to the 41st harmonic of one phase. Then the other two phases can be
analyzed.
The product always yields the RMS values for current and voltage of the fundamental
component for the selected phase. It also provides the total harmonic distortion (THD) for
current and voltage.
From the 40 upper harmonics, 3 can be selected and analyzed at the same time. The
RMS value for current and voltage is calculated for each selected upper harmonic, along
with the harmonic distortion (HD). The 3 upper harmonics can be freely selected, e.g., 4,
12 and 19, or 2, 35 and 40.
Calculation of Power Factors
The power factor
cos phi
is the cosine of the phase angle between voltage and current
for the specific phase. Calculation of the power factor only takes into account the phase
shifting of the fundamental components of voltage and current. The sign of "cos phi" indi-
cates the following:
• Positive (plus) sign: Import of active power from the network
• Negative (minus) sign: Export of active power to the network
The
power factor PF
is the quotient of the active power (P) and apparent power (S) and
takes the entire spectrum into account, i.e., the fundamental component and the upper
harmonics.
PF = P / S
• Positive (plus) sign: Import of active power from the network
• Negative (minus) sign: Export of active power to the network
The
power factor LF
is the quotient of the amount for active power (P) and apparent
power (S), multiplied by the sign of the reactive power (Q), and takes the entire spectrum
into account, i.e., the fundamental component and the upper harmonics: