10.2.5.3 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.
Figure 965: 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
th
harmonic is
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.
The time stamp for the ready 10-minute mean value calculation can be seen in
monitored data L time stamp.
The window type used for the 10-minute mean value calculation is always non-
sliding. The 10-minute value calculation begins based on the protection relay's
internal clock 10 minutes time (for example,11:00, 11:10, 11:20, 11:30, 11:40, 11:50,
12:00…). This is called 10 min tick.
1MRS759142 F
Power quality measurement functions
REX640
Technical Manual
1823
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