Sel 751A, Instruction Manual

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4.61
Date Code 20100129 Instruction Manual SEL-751A Relay
Protection and Logic Functions
Reclose Logic
Lockout State
The reclosing relay goes to the Lockout State if any one of the following
occurs:
➤
The shot counter is equal to or greater than the last shot at time
of reclose initiation (e.g., all automatic reclosing attempts are
unsuccessful—see
Figure 4.32 ).
➤
Reclose initiation is unsuccessful because of SEL
OGIC
control
equation setting 79RIS [see Reclose Initiate and Reclose
Initiate Supervision Settings (79RI and 79RIS, Respectively) on
page 4.66
].
➤
The circuit breaker opens without reclose initiation (e.g., an
external trip).
➤
The shot counter is equal to or greater than last shot, and the
circuit breaker is open [e.g., the shot counter is driven to last
shot with SEL
OGIC
control equation setting 79DLS while open
interval timing is in progress. See Drive-to-Lockout and Drive-
to-Last Shot Settings (79DTL and 79DLS, Respectively) on
page 4.68
].
➤
The close failure timer (setting CFD) times out (see
Figure 4.30 ).
➤
SEL
OGIC
control equation setting 79DTL = logical 1 [see
Drive-to-Lockout and Drive-to-Last Shot Settings (79DTL and
79DLS, Respectively)
].
➤
The Reclose Supervision Limit Timer (setting 79CLSD) times
out (see
Figure 4.31 and top of Figure 4.32 ) and the reclose
enable setting, E79, has setting choices 1, 2, 3, or 4.
➤
A new reclose initiation occurs while the reclosing relay is
timing on an open interval (e.g., flashover in the tank while
breaker is open).
The OPEN command is included in the reclosing relay logic via the factory
SEL
OGIC
control equation settings:
79DTL := OC OR ... (drive-to-lockout)
Relay Word bit OC asserts for execution of the OPEN command. See OPEN
Command (Open Breaker) on page 7.33 for more information on the OPEN
command. Also, see Drive-to-Lockout and Drive-to-Last Shot Settings
(79DTL and 79DLS, Respectively) on page 4.68 .
Reclosing Relay
States and Settings/
Setting Group
Changes
If individual settings are changed for the active setting group or the active
setting group is changed, all of the following occur:
➤
The reclosing relay remains in the state it was in before the
settings change.
➤
The shot counter is driven to last shot (last shot corresponding
to the new settings; see discussion on last shot that follows).
➤
The reset timer is loaded with reset time setting 79RSLD (see
discussion on reset timing later in this section).