Landis+Gyr E650 Series User Manual page 20

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
Calculation method 2
(from rms values)

Summation channels
Power factor cosφ
Phase voltages
Phase currents
Neutral current
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Only fundamental wave considered for reactive energy
Only the fundamental wave is considered for the calculation of the reactive
energy share; possible harmonics are not taken into account.
From the mean values U1
microprocessor calculates by multiplication the apparent power of the
individual phases ±VA1, ±VA2 and ±VA3 and summates these for the total
apparent power ±VA.
Mean values
per second
I 1
rm s
I 1 U1
å
rm s rm s
U 1
rm s
I 2
rm s
I 2 U2
å
rm s rm s
U 2
rm s
I 3
rm s
I 3 U3
å
rm s rm s
U 3
rm s
Figure 12. Total apparent power according to calculation method 2 (ZxD300Cx
combi-meters only)
Harmonics considered for reactive energy
As RMS values are used for the calculation of the apparent energy with
calculation method 2, not only the fundamental wave but also the
harmonics are taken into account. Therefore, if harmonics are present, the
measured values are greater than those of calculation method 1.
The values of two measurement quantities (incl. pulse inputs EX1 and EX2)
can be added.
The power factor cosφ is calculated in combi-meters as follows:
The meter uses the method of calculation employed for calculating the
apparent power.
The rms values of the voltages U1
the mean values of the squares of the voltages by extracting the root and
directly from these the phase voltages U1, U2 and U3.
The rms values of the currents I1
mean values of the squares of the currents by extracting the root and
directly from these the phase currents I1, I2 and I3.
The signal processor calculates the instantaneous neutral current i0 by
adding the instantaneous phase currents i1, i2 and i3.
i2
i0 = i1 + i2 + i3
i1 (vectorial addition)
i3
i0
Figure 13. Neutral current I
, U2 , U3 and I1
rms rms rms




, U2 and U3
rms rms
, I2 and I3
rms rms
0
D000030108 en m – E650 Series 3 – ZMD300AT/CT – User Manual
Device description
, I2 , I3 the
rms rms rms
Measured quantities
+S (Import)
-S (Export)
are obtained from
rms
are obtained from the
rms