Sel 551 - Close Logic

3.20
SEL-551 Relay Instruction Manual Date Code 20110408
Relay Elements and Logic
Close Logic
Close Logic
The close logic in Figure 3.14 provides flexible circuit breaker closing/auto
reclosing with SEL
OGIC control equation settings:
CL (close conditions, other than automatic reclosing or CLOSE
command)
ULCL. (unlatch close conditions, other than breaker status, close failure, or
reclose initiation)
52A (breaker status)
and setting:
CFD (Close Failure Time)
Figure 3.14 Close Logic
Set Close
If all the following are true:
➤ The unlatch close condition is not asserted (ULCL = logical 0),
➤ The circuit breaker is open (52A = logical 0),
➤ The reclose initiation condition (79RI) is not making a rising
edge (logical 0 to logical 1) transition,
➤ And a close failure condition does not exist (Relay Word bit CF
= 0),
then the CLOSE Relay Word bit can be asserted to logical 1 if any one of the
following occurs:
➤ The serial communications port CLOSE command is executed,
➤ A reclosing relay open interval times out,
➤ Or SELOGIC control equation setting CL goes from logical 0 to
logical 1 (rising edge transition).
Close Failure
Timer
CF
Rising Edge Detect
ULCL
Reclosing Relay
Open Interval
Time-Out
79RI
52A
CL
SEL
OGIC
Settings
CLOSE
Relay
Word
Bits
Pulses (logical 1)
for one processing
interval if Close
Failure Timer
times out (drives
reclosing relay to
lockout)
CFD
0
CLOSE
Command
Logical 1 (setting
CFD 0; Close Failure
Timer Operative)
Logical 0 (setting
CFD = 0; Close Failure
Timer Inoperative)