CMC 356 Reference Manual
84
6.11.6.5 Accuracy
of
Power
Measurement
General
The power is calculated from one current channel and one voltage channel:
Active power:
[W]
Apparent power:
S = V
rms
x I
rms
[VA]
Reactive power:
[var]
U
rms
=
, I
rms
=
Accuracies
Conditions: integration time 1s, measurement signal sinusoidal, excitation
10-100 %, accuracy references the apparent power, error of the current
clamp is not taken into account.
Table 6-41:
Sampling rates
28.44kHz
9.48kHz
3.16kHz
Table 6-42:
Sampling rate
28.44kHz
P
1
T
---
=
*
u t
( )
*
i t
( )
t
d
0
T
Q
S
2
P
2
–
=
*sign_Q
1
T
---*
u t
( )
2
t
d
0
T
1
T
---*
i t
( )
2
t
d
0
T
Frequency range
Power
Accuracy
1
AC
Typical
Guaranteed
10 Hz ... 100 Hz
S
± 0.3 %
± 0.7 %
P
± 0.3 %
± 0.7 %
Q
± 0.8 %
± 2 %
Frequency range
Power
Accuracy
1
1
S = Apparent power
P = Active power
Q = Reactive power
AC
Typical
Guaranteed
10 Hz ... 2.2 kHz
S
+ 0.3 % / - 1.2 %
± 2.5 %
P
+ 0.3 % / - 1,2 %
± 2.5 %
Q
+ 0.8 % / - 2.5 %
± 3.5 %
Actual - Expected
Full scale
x 100 %
Relative error:
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