Figure. 5.4.3. - 18. Simpli ed function block diagram of the DOC function.
Measured input values
Function block uses analog current measurement values. Function block always utilizes peak-to-peak
measurement from samples and by user selection the monitored magnitude can be either fundamental
frequency RMS values, True RMS values from the whole harmonic specter of 32 components or peak-
to-peak values. -20ms averaged value of the selected magnitude is used for pre-fault data registering.
Fault current angle is based on comparison of positive sequence voltage U1 and positive sequence
current I1. If positive sequence voltage is not available (3 line-to-line voltages but no U0) voltage angle
is based on faulty phase line to line voltage. In case voltage drops below 1V in the secondary side
during fault, voltage memory is used for 0.5 seconds. When 0.5 exceeds the reference angle of voltage
is forced to 0°.
Table. 5.4.3. - 61. Analogic magnitudes used by the DOC function.
Signal
Description
Time base
IL1PP
Peak-to-peak measurement of phase L1/A current
5 ms
IL2PP
Peak-to-peak measurement of phase L2/B current
5 ms
IL3PP
Peak-to-peak measurement of phase L3/C current
5 ms
IL1RMS
Fundamental RMS measurement of phase L1/A current
5 ms
IL2RMS
Fundamental RMS measurement of phase L2/B current
5 ms
IL3RMS
Fundamental RMS measurement of phase L3/C current
5 ms
IL1TRMS
TRMS measurement of phase L1/A current
5 ms
IL2TRMS
TRMS measurement of phase L2/B current
5 ms
IL3TRMS
TRMS measurement of phase L3/C current
5 ms
U
1
RMS
Fundamental RMS measurement of voltage U
1
/V
5 ms
U
2
RMS
Fundamental RMS measurement of voltage U
2
/V
5 ms
U
3
RMS
Fundamental RMS measurement of voltage U
3
/V
5 ms
U
4
RMS
Fundamental RMS measurement of voltage U
4
/V
5 ms
AQ-T257
Instruction manual
Version: 2.00
© Arcteq Relays Ltd
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