4.68
SEL-751A Relay
Instruction Manual
Date Code 20100129
Protection and Logic Functions
Reclose Logic
If the following setting is made:
79RI :=
0
(numeral 0)
reclosing will never take place (reclosing is never initiated). The reclosing
relay is effectively inoperative.
If the following setting is made:
79RIS :=
0
(numeral 0)
reclosing will never take place (the reclosing relay goes directly to the lockout
state any time reclosing is initiated). The reclosing relay is effectively
inoperative.
Drive-to-Lockout and
Drive-to-Last Shot
Settings (79DTL and
79DLS, Respectively)
When 79DTL = logical 1, the reclosing relay goes to the Lockout State (Relay
Word bit 79LO = logical 1), and the front-panel
LO
(Lockout) LED
illuminates.
79DTL has a 1 second dropout time. This keeps the drive-to-lockout condition
up 1 second after 79DTL has reverted back to 79DTL = logical 0. This is
useful for situations where both of the following are true:
➤
Any of the trip and drive-to-lockout conditions are “pulsed”
conditions (e.g., the
OPEN
command Relay Word bit, OC,
asserts for only 1/4 cycle—refer to
➤
Reclose initiation is by the breaker contact opening (e.g., 79RI
:= NOT 52A—refer to
Additional Settings Example on
).
Then the drive-to-lockout condition overlaps reclose initiation and the
SEL-751A stays in lockout after the breaker trips open.
When 79DLS = logical 1, the reclosing relay goes to the last shot, if the shot
counter is not at a shot value greater than or equal to the calculated last shot
(see
Reclosing Relay Shot Counter on page 4.66
).
EXAMPLE 4.9
Factory Settings Example
The drive-to-lockout factory setting is:
79DTL :=
OC OR SV04T
Relay Word bit OC asserts for execution of the OPEN command. See
the Note in the Lockout State discussion, following
Relay Word bit SV04T asserts for execution of the open command
from front panel push button (see
for more
detail).
The drive-to-last shot factory setting is:
79DLS :=
79LO
One open interval is also set in the factory settings, resulting in last
shot = 1. Any time the relay is in the lockout state (Relay Word bit
79LO = logical 1), the relay is driven to last shot (if the shot counter is
not already at a shot value greater than or equal to shot = 1):
79DLS :=
79LO
= logical 1
Thus, the relay is driven to the Lockout State (by setting 79DTL) and,
subsequently, last shot (by setting 79DLS).
Содержание 751A
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