ABB RELION REX640 Technical Manual page 1622

Section 10
Power quality measurement functions
1616
Harmonic calculation
Harmonic mean values are calculated for each phase. Also, the mean values of the
nominal frequency (fundamental) and direct current component are calculated. The
fundamental frequency mean values are shown as percentage of the nominal phase-to-
earth voltage.
The actual harmonic mean values are shown as percentage of the fundamental voltage.
When the reference voltage (the fundamental voltage) is extremely low (below 0.02
xUn), the calculation is blocked internally. As a result, value zero is used in the mean
value calculation of individual harmonics. Extremely high harmonic values are
limited to 2.0 xUn.
The calculation window length is set with the Sliding interval setting. It has three
window lengths ("3 seconds", "1 minute" or "5 minutes") for shorter mean value
outputs. Output values can also be seen in the monitored data.
The window type used for configuration tool output values is always sliding. Output
values are updated once every 0.1 seconds.
GUID-088882B9-93C3-43B8-81D3-1638399426C0 V1 EN
Figure 833: Sliding 3 seconds value calculation in principle
The shorter mean values of the fundamental of each phase are SMNH01_A,
SMNH01_B and SMNH01_C. Actual harmonics are seen with their number, for
example, phase A for second harmonic is SMNH02_A and phase C for 9
SMNH09_C. Direct current component outputs are SMNDC_A, SMNDC_B and
SMNDC_C.
Intervals that are longer than 3 seconds are calculated using free running 3-second
mean values.
The longer 10-minute mean values of the fundamental of each phase are seen in
monitored data as LMNH01_A, LMNH01_B and LMNH01_C. Actual harmonics are
seen with their number. Direct current components are LMNDC_A, LMNDC_B and
LMNDC_C.
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REX640
Technical Manual