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6.6. Configuration of THD Measurement,
Harmonics and Energy for the Harmonic
The meter has 3 work modes related to the THD and harmonic calculation.
When setting the parameter of the harmonic number:
- tHd – the meter measures every 1 second only the THD value for currents
and voltages, the result is exposed on the display and expressed in
registers in percentages. Energy of harmonics is reset and particular
harmonics include the error value (1e20);
- All – the meter measures harmonics from 2 up to 21, for 50 Hz frequency
(from 2 up to 18 for 60 Hz frequency). Energy of harmonics is reset.
- 2 – 21 – measurement of the selected harmonic value, every 1 second,
the result is exposed on the display and in basic units (V, A) in registers.
Energy for the given harmonic is counted up.
The switching of the harmonic number or the change of voltage or current
ratio resets energy for harmonics.
6.7. Archive – Active Power Profile
The ND20 meter is equipped with an archive allowing to store up to
9000 measurements of mean active power. Mean active power PAV is
archived with a 15, 30, 60 minutes’ interval of time, synchronized with the
real time clock. In case of operation in the 15 minutes’ walking window
mode, the archiving is performed in the same way as for the 15 minutes’
interval of time (fig. 11). The direct access to the archive is for 15 records
including the date, time and value placed in the range of addresses
1000 -1077. The position of the first (oldest) archived sample is placed
in the register 1000, however the position of the last archived sample
(youngest) is placed in the register 1001. the value of the first record,
from 15 available records placed in registers 1003 – 1077, is written in
the register 1002. The write of the first read out record value (1 – 9000)
causes the data updating of 15 records for readout.
In registers, in which samples were not already been written, are 1e20
values.
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