Siemens Sicam P850 7KG85 Series - Measuring and Recording System; Functioning of the Measuring System According to IEC 61000-4-30

4 Measurands and Recording
4.1 Measuring and Recording System
30 SICAM P850/P855, 7KG85xx, Device Manual
E50417-H1040-C482-A6, Edition 10.2018
4.1 Measuring and Recording System
4.1.1 Functioning of the Measuring System according to IEC 61000-4-30
SICAM P850/P855 devices measure the power quality according to IEC 61000-4-30 in 1-phase or multi-phase
distribution systems. The measuring system is implemented according to class A. In terms of functional scope,
measuring ranges, and accuracy, the SICAM P850/P855 devices are class S.
The basic measuring interval for determining the values for mains voltage, harmonics of mains voltage, and
mains voltage unbalance is a 10-period time interval for 50-Hz distribution systems or a 12-period time interval
for 60-Hz distribution systems. The measurement of the 10-/12-period time intervals is resynchronized at each
RTC 10-minute limit.
Subsequently, the values for the 10-/12-period time intervals are aggregated over additional time intervals (for
example, 10-minute interval at SICAM P850/P855).
10-Minute Interval (SICAM P850/P855)
The value aggregated in a 10-minute interval is tagged with the absolute time (for example 01:10:00). The time
at the end of the aggregation interval is indicated as the time qualifier. The values for the 10-minute time interval
are calculated without interruption from the 10-/12-period time intervals.
• Each 10-minute interval begins at an RTC 10-minute limit. At this 10-minute limit, the 10-/12-period time
intervals are aggregated over a 10-minute interval. The last 10-/12-period time interval in a 10-minute
aggregation interval overlaps in time at an RTC 10-minute limit. Each overlapping 10-/12-period time
interval (for the overlapping area, see Figure 4-1) is included in the aggregation interval of the preceding
10-minute interval.
• The aggregation interval enables the power system quality to be evaluated according to EN 50160. The
aggregation interval can be adjusted to other applications using a parameter. A shorter aggregation
interval increases the storage capacity required for measured values and reduces the maximum possible
recording time in the memory.
Figure 4-1 Synchronization of the Aggregation Intervals for Class A
RTC
10-minute
limit
k
10-minute interval (x+1)
j
10/12 periods
i
1
2 3
Overlapping area
10-minute interval (x)
10/12 periods
10/12 periods 10/12 periods
10/12 periods
10/12 periods