I2>: Level of high negative sequence current detection given in % of IBase. This
setting should be based on fault calculations to find the negative sequence current
in case of a fault at the most remote point where the direct trip scheme shall be
active. The negative sequence current shall be calculated for different types of
faults (single phase to earth, phase to phase to earth and phase to phase short
circuits) at different switching states in the network.
tI2: Time delay for trip in case of high negative sequence 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.
16.8.10 Zero sequence overcurrent protection LCZSPTOC
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16.8.10.1 Identification
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Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Zero sequence overcurrent protection
LCZSPTOC - 51N
16.8.10.2 Application
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Zero sequence symmetrical components are present in all abnormal conditions
involving earth. They are having a considerably high value during earth faults.
Zero sequence overcurrent protection (LCZSPTOC) is a definite time stage
comparator function. The zero sequence input current from the SMAI block is
connected as input to the function through a group connection I3P in PCM600.
This current is compared against the preset value and a start signal will be set high
if the input zero sequence current is more than the preset value 3I0>. Trip signal
will be set high after a time delay setting of t3I0. BLOCK input will block the
complete function. BLKTR will block the trip output. Zero sequence current is
available as service value output 3I0.
16.8.10.3 Setting guidelines
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GlobalBaseSel: Selects the global base value group used by the function to define
IBase, UBase and SBase as applicable.
3I0> : Level of high zero sequence current detection given in % of IBase. This
setting should be based on fault calculations to find the zero sequence current in
case of a fault at the most remote point where the direct trip scheme shall be active.
The zero sequence current shall be calculated for different types of faults (single
Section 16 1MRK 506 369-UEN B
Scheme communication
738 Line distance protection REL670 2.2 IEC
Application manual
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