Table. 5.2.1 - 23. Harmonic current measurements.
Name
Unit
Range
Step Default
Description
Harmonics
calculation
values
("Harm Abs.pr
Perc.")
-
0: Percent
1: Absolute
-
0:
Percent
Defines whether the harmonics are calculated as
percentage or absolute values.
Harmonics
display
-
0: Per unit
1: Primary A
2: Secondary A
-
0: Per
unit
Defines how the harmonics are displayed: in p.u. values,
as primary current values, or as secondary current
values.
Maximum
harmonics value
("IxxMaximum
harmonic")
A
0.000…1000000.000 0.001 -
Displays the maximum harmonics value of the selected
current input ILx or I0x.
Fundamental
frequency
("Ixx
fundamental")
A
0.000…1000000.000 0.001 -
Displays the current value of the fundamental frequency
measurement (RMS) from the selected current input ILx
or I0x.
Ixx harmonics
(2
nd
…31
st
harmonic)
A
0.000…1000000.000 0.001 -
Displays the selected harmonic from the current input
ILx or I0x.
5.2.2 Frequency tracking and scaling
Measurement sampling can be set to the frequency tracking mode or to the fixed user-
defined frequency sampling mode. The benefit of frequency tracking is that the measurements are
within a pre-defined accuracy range even when the fundamental frequency of the power system
changes.
Table. 5.2.2 - 24. Frequency tracking effect (FF changes from 6 Hz to 75 Hz).
The measurement error with a fixed 50 Hz sampling frequency
when the frequency changes. The constant current is 5 A, the
frequency sweep is from 6 Hz to 75 Hz.
The measurement error with frequency tracking when the
frequency changes. The constant current is 5 A, the
frequency sweep is from 6 Hz to 75 Hz.
As the figures above show, the sampling frequency has a major effect on the relay's measurement
accuracy. If the sampling is not tracked to the system frequency, for example a 10 Hz difference
between the measured and the set system frequency can give a measurement error of over 5 %. The
figures also show that when the frequency is tracked and the sampling is adjusted according to the
detected system frequency, the measurement accuracy has an approximate error of 0.1...- 0.2 % error
in the whole frequency range.
A
AQ
Q-T256
-T256
Instruction manual
Version: 2.06
© Arcteq Relays Ltd
IM00028
27
Summary of Contents for AQ-T256
Page 1: ...AQ T256 Transformer protection IED Instruction manual...
Page 2: ......
