4.135
Date Code 20170927 Instruction Manual SEL-751 Relay
Protection and Logic Functions
Group Settings (SET Command)
Set Reclose Supervision Logic.
Refer to the bottom of Figure 4.81. If all the following are true:
➤ The close logic output CLOSE (also see Figure 4.80) is not
asserted (Relay Word bit CLOSE = logical 0).
➤ The reclosing relay is not in the lockout state (Relay Word bit
79LO = 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.
➤ The Reclose Supervision Limit Timer is not timed out (Relay
Word bit RCSF = logical 0).
then a reclosing relay open interval time-out seals as shown in Figure 4.81.
Then, when 79CLS asserts to logical 1, the sealed-in reclosing relay open
interval time-out condition propagates through Figure 4.75 and on to the close
logic in Figure 4.80.
Unlatch Reclose Supervision Logic.
Refer to the bottom of Figure 4.81. If the reclosing relay open interval time-
out condition is sealed-in, it stays sealed-in until one of the following occurs:
➤ The close logic output CLOSE (also see Figure 4.81) asserts
(Relay Word bit CLOSE = logical 1).
➤ The reclosing relay goes to the lockout state (Relay Word bit
79LO = logical 1).
➤ The circuit breaker closes (52A = logical 1).
➤ The reclose initiation condition (79RI) makes a rising-edge
(logical 0 to logical 1) transition.
➤ SELOGIC control equation setting 79CLS asserts
(79CLS = logical 1).
➤ The Reclose Supervision Limit Timer times out (Relay Word
bit RCSF = logical 1 for one processing interval).
The Reclose Supervision Limit Timer is inoperative if setting
79CLSD := OFF. With 79CLSD := OFF, reclose supervision condition 79CLS
is not time limited. When an open interval times out, reclose supervision con-
dition 79CLS is checked indefinitely until one of the other unlatch conditions
listed previously comes true.
The unlatching of the sealed-in reclosing relay open interval time-out condi-
tion by the assertion of SEL
OGIC control equation setting 79CLS indicates
successful propagation of a reclosing relay open interval time-out condition on
to the close logic in Figure 4.80. See Example 4.18.
EXAMPLE 4.17 Settings Example 1
Refer to the top of Figure 4.81 and Figure 4.83.
SEL-751 Relays are installed at both ends of a transmission line in a high-
speed reclose scheme. After both circuit breakers open for a line fault, the
SEL-751 (1) recloses circuit breaker 52/1 first, followed by the SEL-751(2)
reclosing circuit breaker 52/2, after a synchronism check across circuit
breaker 52/2.
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