METREL MI 2893 - Page 201

MI 2893 / MI 2892 / MI 2885 Measurement methods
201
RTC
End of
Interval
10/12 cycles 10/12 cycles 10/12 cycles
10/12 cycles 10/12 cycles 10/12 cycles
1 2 3i j k
overlap
10 min interval (x)
10 min interval (x+1)
Figure 164: Synchronization and aggregation of 10/12 cycle intervals
Depending from the quantity, for each aggregation interval instrument computes average, minimal,
maximal and/or active average value, this can be RMS (root means square) or arithmetical average.
Equations for both averages are shown below.
RMS average



N
j
jRMS
A
N
A
1
2
1
Where:
A
RMS
– quantity average over given aggregation interval
A – 10/12-cycle quantity value
N – number of 10/12 cycles measurements per aggregation interval.
(73)
Arithmetic average:



N
j
javg
A
N
A
1
1
Where:
A
avg
– quantity average over given aggregation interval
A – 10/12-cycle quantity value
N – number of 10/12 cycles measurements per aggregation interval.
(74)
In the next table averaging method for each quantity is specified:
Table 141: Data aggregation methods
Group
Value
Aggregation method
Recorded values
Voltage
U
Rms
RMS average
Min, Avg, AvgOn, Max
THD
U
RMS average
AvgOn, Max
CF
U
RMS average
Min, Avg, Max
Current
I
Rms
RMS average
Min, Avg, AvgOn, Max
THD
I
RMS average
Avg, AvgOn, Max
CF
I
RMS average
Min, Avg, AvgOn, Max
Frequency
f(10s)
-
AvgOn
f(200ms)
RMS average
Min, AvgOn, Max