5 Theory and internal operation
75
5 Theory and internal operation
This section contains basics theory of measuring functions and technical information of
the internal operation of the PowerQ4 instrument, including descriptions of measuring
methods and logging principles.
5.1 Measurement
methods
5.1.1 Measurement aggregation over time intervals
Standard compliance: IEC 61000-4-30 Class S (Section 4.4)
The basic measurement time interval for:
•
Voltage
•
Current
•
Active, reactive and apparent power
•
Harmonics
•
Unbalance
is 10-cycle time interval. The 10/12-cycle measurement is resynchronized on each
Interval tick according to the IEC 61000-4-30 Class S. Measurement methods are
based on the digital sampling of the input signals, synchronised to the fundamental
frequency. Each input (4 voltages and 4 currents) is simultaneously sampled 1024 times
in 10 cycles.
5.1.2 Voltage measurement (magnitude of supply voltage)
Standard compliance: IEC 61000-4-30 Class S (Section 5.2)
All voltage measurements represent RMS values of 1024 samples of the voltage
magnitude over a 10-cycle time interval. Every 10 interval is contiguous, and not
overlapping with adjacent 10 intervals.
U1
U2
U3
UN
U1
2
U23
U31
Figure 5.1: Phase and phase-to-phase (line) voltage
Voltage values are measured according to the following equation:
Phase voltage:
∑
=
=
1024
1
2
1024
1
j
j
p
p
u
U
[V], p: 1,2,3,N
(1)