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Measuring and Recording
3.2 Measurement and Evaluation Functions
The following values are given for each harmonic:
•
RMS value (for power: RMS value and sign)
•
Phase angle
The sign of the active power of the single harmonic can indicate the direction of the power flow of this
harmonic in a supply system – seen from the installation point of the device. Thus, it is possible to identify
demands that generate the harmonics and that are probably the cause of the harmonics.
For the voltage and current, the given phase angle of the harmonic refers to the voltage of the fundamental
component in the respective phase. The phase angle between the current harmonic and the corresponding
voltage harmonic is used to calculate the sign of the active harmonic power.
[dw_harmonic directions, 1, en_US]
Figure 3-4
For measuring the RMS values and the phase angles, a 10-cycle interval is used for 50-Hz distribution systems.
For 60-Hz distribution systems, a 12-cycle interval is used.
For the active power of the aggregated harmonics, the following factors are used to caluculate the direction:
•
The aggregated voltage harmonics (average only)
•
The aggregated current harmonics (average only)
•
The prevailing angles including the prevailing factors at the end of each aggregation interval
The sign of the active power of the aggregated harmonics shows the direction:
•
Positive sign: demand side, shown in green on the HTML page
•
Negative sign: supply side, shown in blue on the HTML page
The prevailing factors of the voltage and current harmonics are used to calculate the confidence of the
harmonics power direction. The confidence determines whether the direction is stable or not. If the confi-
dence is lower than 0.91, the direction of the aggregated harmonic power is not shown in the diagram.
The aggregated harmonics power values are shown on the HMTL page. The aggregated harmonics power
values and the confidence values are stored in the PQDIF file.
Measured Quantity
Active Power
Pa
Pb
Pc
Interfaces: protocols IEC 61850 (PQDIF depending on the measuring interval)
104
Principle of Harmonic Directions
Measurement Recorder
Aggregated Value
PQDIF
Measurement Recorder
Confidence Value
PQDIF
x
x
x
SICAM, SICAM Q100 7KG95xx, Manual
E50417-H1040-C522-A9, Edition 06.2021
x
x
x
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