15.8.3.2
Application
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Low active power and power factor protection (LAPPGAPC) is one of the local criteria to be
checked in direct transfer trip (DTT) scheme. In LAPPGAPC, active power and power factor are
calculated from the voltage and current values at this end. On detection of low active power or
low power factor condition, the trip output will be set. All the calculation and comparison are
done per phase.
If there is a fault and the remote end circuit breaker is tripped, a carrier signal is sent to the
local end and the active power in respective phases will decrease. Hence, detection of low
active power in at least one of the phases would be one of the factors to ascertain the fault at
other end.
The function has two modes, '1 out of 3' and '2 out of 3'. '1 out of 3' mode ensures that there is
low active power in at least one of the three phases, while the '2 out of 3' mode the low power
is ensured in at least two phases simultaneously before sending the trip signal.
Line which is tripped at the remote end will have low active power flowing through it which
also results in low power factor in the respective phase. A low power factor criterion could also
be an added check of the local criterion in DTT. In this function phase wise power factor is
calculated, and a comparison is made for the low power factor condition to give phase
segregated start and trip.
15.8.3.3
Setting guidelines
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GlobalBaseSel: Selects the global base value group used by the function to define (IBase),
(
UBase) and (SBase).
OperationLAP: Used to set the low power function On or Off.
OpMode: Can be set 2 out of 3 or 1 out of 3. If 1 out of 3 is set, the function will send TRIP signal
if one or more phases have low power. If
2 out of 3 is set, the function will send TRIP signal if
two or more phases have low power. When the remote breaker has opened, there should
theoretically be zero power at the protection measurement point. However, when fault current
is fed to the fault point the power loss in the fault will be detected. For operation for all
unsymmetrical faults
1 out of 3 should be selected.
LAP<: Level of low active power detection, given in % of SBase. This parameter should be set
as low as possible to avoid activation during low load conditions at undisturbed network
operation. The measurement is blocked for current levels below 3 % of
IBase and 30% of
UBase. All outputs are blocked.
tOpLAP: Time delay for trip in case of low active power detection.
OperationLPF: Used to set the low power factor function On or Off.
LPF<: Level of low power factor detection. The setting should be set lower than the lowest
power factor at undisturbed network operation. A value lower than
0.4 is normally sufficient.
tOpLPF: Time delay for trip in case of low power factor detection.
15.8.4
Compensated over and undervoltage protection COUVGAPC
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1MRK 505 343-UEN B
Section 15
Scheme communication
623
Application manual
Содержание Relion 670 series
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