Name
M#
3PH (S)
20.00
3PH (P)
17.32
3PH (Q)
0.00
3PH Tan
0.00
3PH Cos
0.87
5.2.4. Frequency tracking and scaling
Measurement sampling can be set to frequency tracking mode or xed user given frequency sampling
mode. Bene t of the frequency tracking is that the measurements are in given accuracy range even
when the fundamental frequency of the power system changes.
Table. 5.2.4. - 49. Frequency tracking effect when the fundamental frequency is changing from 6 Hz to 75 Hz.
Measurement error with xed 50Hz sampling frequency when
frequency changes. Constant current of 5A, frequency sweep
from 6 Hz to 75 Hz
Measurement error with frequency tracking when
frequency changes. Constant current of 5A, frequency
sweep from 6 Hz to 75 Hz
As can be seen in the gure above the sampling frequency has major effect to the measurement
accuracy of the IED. If the sampling is not tracked to the system frequency it can be seen that even a
change from set 50Hz to measured system frequency 60Hz (most common system frequencies)
already gives measurement error of roughly over 5% in the measured phase currents. From the gure
can also be seen that when the frequency is tracked the measurement accuracy is about -0.2% - 0.1%
error in the whole frequency range when the sampling is adjusted according to the detected system
frequency.
AQ-F255
Instruction manual
Version: 2.00
© Arcteq Relays Ltd
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