Siemens SIMEAS R-PMU, Manual, Page: 42 / 296

6
6.1 Measured Value Acquisition and Processing
42
Digital Fault Recorder, SIMEAS R-PMU, Manual
E50417-H1076-C360-A5, Release 10.2012
6.1 Measured Value Acquisition and Processing
Figure 6-1 Measured value acquisition and processing
Sampling
AC and process signals of a data acquisition unit are digitized with a constant sampling rate of
192 sample values per nominal cycle. The binary signals are also read with a constant sampling
rate of 2 kHz and stored.
For further processing, the frequency is calculated first and then used to resample the sample
values.
This is not applicable for process values. Process values are zero-frequency values and are
therefore processed separately.
Nominal cycle duration
The nominal cycle duration T
n
is the reciprocal of the nominal system frequency f
n
: T
n
= 1/f
n
.
With a nominal system frequency of, e. g., 50 Hz, the nominal cycle duration is 20 ms. The cur-
rently measured cycle may differ from the nominal cycle.
Sam pling AC signals
DC signals
Binary signals
Sam pling
Sam pling
Calculation of half- cycle
rm s values
FFT
M easured and
trigger values
M easured and
trigger values
Trigger value
M easured value
M easured and
trigger values
M ean value calculation
Resam pling
Frequency calculation
M easured value
M easured and
trigger values