16.8.11.2 Application
Three phase overcurrent (LCP3PTOC, 51) is designed for detecting over current
conditions due to fault or any other abnormality in the system.
LCP3PTOC (51) could be used as a back up for other local criterion checks.
16.8.11.3 Setting guidelines
GlobalBaseSel: Selects the global base value group used by the function to define IBase,
VBase and SBase as applicable.
PU 51: Level of high phase current detection given in % of IBase. This setting can be
based on evaluation of the largest current that can occur during non-faulted network
operation: I
loadmax
. Fault calculations where the smallest current at relevant faults gives:
I
faultmin
. The setting can be chosen: I
loadmax
<IOC> <I
faultmin
tOC: Time delay for trip in case of high phase current detection. The trip function can be
used as stand alone short circuit protection with a long time delay. The choice of time
delay is depending on the application of the protection as well as network topology.
16.8.12 Three phase undercurrent LCP3PTUC (37)
16.8.12.1 Identification
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Three phase undercurrent
LCP3PTUC - 37
16.8.12.2 Application
Three phase undercurrent protection function (LCP3PTUC, 37) is designed for detecting
loss of load conditions.
When the transformer or shunt reactor differential operates and the secondary side circuit
breaker is tripped there will be very low current from this end of the line to the remote end.
LCP3PTUC (37) detects the above low current condition by monitoring the current and
helps to trip the circuit breaker at this end instantaneously or after a time delay according
to the requirement.
Section 16 1MRK 506 369-UUS -
Scheme communication
788 Line distance protection REL670 2.2 ANSI
Application manual
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