Landis+Gyr E650 Series User Manual page 16

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U , I calculation
RMS RMS
Time measurement
Mean value formation
© Landis+Gyr
component is the product of the voltage component with the current
component vertical to the voltage). Thereby no harmonics are measured
since only the fundamental wave is rotated through 90°.
I
Q
I

I
P
Figure 6. Reactive power calculation (method: measured)
Calculated vectorial (not recommended):
The instantaneous value of reactive power is calculated using the values of
active power and apparent power.
The reactive power is the square root of the square value of apparent
power minus the square value of active power. This method includes the
harmonics.
The square values of voltage and current are obtained by multiplying the
instantaneous values of voltage and current by themselves. From these
values the signal processor forms the corresponding single-phase RMS
values U and I
RMS RMS
The network frequency can be calculated from the time measured between
two zero passages (change from negative to positive value of voltage U1).
The times between zero passage of the phase voltage U1 and those of the
other phase voltages U2 and U3 serves to determine the phase angle
between the voltages and of the rotating field.
U1 U2 U3
1
2
3
Figure 7. Time measurement
The phase angle between voltage and current is determined by the times
between zero passage of the phase voltage U1 and those of the phase
currents I1, I2 and I3.
For further processing of the individual signal, the signal processor
generates mean values over one second, which the following
microprocessor scans at intervals of one second.
Calculation per phase of
. .
Q = U I sin
U
.
Time measurement
for rotating field,
frequency, phase angle
1 : T
2 : T
3 : T
D000030108 en m – E650 Series 3 – ZMD300AT/CT – User Manual
Device description

U1-U2
U1-U3
(fn)
U1-U1