ABB Relion 670 series - Introduction; Principle of operation; Function block; Input and output signals

13.8.9.1 Introduction
Zero sequence components are present in all abnormal conditions involving ground.
They have a considerably high value during ground faults.
13.8.9.2 Principle of operation
Zero sequence overcurrent protection (LCZSPTOC, 51N) 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 pickup signal will be set high if the
input zero sequence current is greater than the preset value 3I0 PU. 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. The zero sequence current is available as
service value output 3I0.
13.8.9.3 Function block
ANSI09000770-1-en.vsd
LCZSPTOC (51N)
I3P*
BLOCK
BLKTR
TRIP
RI
ANSI09000770 V1 EN
Figure 424: LCZSPTOC (51N) Function block
13.8.9.4 Input and output signals
Table 479: LCZSPTOC (51N) Input signals
Name
Type Default Description
I3P GROUP
SIGNAL
- Three phase group signal for current inputs
BLOCK BOOLEAN 0 Block overall function
BLKTR BOOLEAN 0 Block trip output
Table 480: LCZSPTOC (51N) Output signals
Name
Type Description
TRIP BOOLEAN Trip signal for zero sequence over current protection
RI BOOLEAN Start signal for zero sequence over current protection
1MRK505222-UUS C Section 13
Scheme communication
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Technical reference manual