5 Theory and internal operation
86
A new recording interval commence after previous interval run out, at the beginning of
the next 10 cycle time interval. The data for the IP time interval are aggregated from 10-
cycle time intervals, according to the figure bellow. The aggregated interval is tagged
with the absolute time. The time tag is the time at the conclusion of the interval. There is
no gap or overlap, during recording, as illustrated on figure bellow.
Figure 5.9: Synchronization and aggregation of 10 cycle intervals
For each aggregation interval instrument computes average value for measured
quantity. Depending from the quantity, this can be (root means square) or arithmetical
average. Equations for both averages are shown bellow.
RMS average
∑
=
=
N
j
j
RMS
A
N
A
1
2
1
,
Where:
A
RMS
– quantity average over given aggregation interval
A – 10-cycle quantity value
N – number of 10 cycles measurements per aggregation interval.
(26)
Arithmetic average:
∑
=
=
N
j
j
avg
A
N
A
1
1
Where:
A
avg
– quantity average over given aggregation interval
A – 10-cycle quantity value
N – number of 10 cycles measurements per aggregation interval.
(27)
In the next table averaging method for each quantity is specified:
Table 5.3: Data aggregation methods
Group
Value
Aggregation method
U
Rms
RMS
THD
U
RMS
Voltage
U
cf
Arithmetic
Current
I
Rms
RMS
