4.140
SEL-751 Relay Instruction Manual Date Code 20170927
Protection and Logic Functions
Group Settings (SET Command)
Relay Word bit OC asserts for execution of the OPEN command. See OPEN
Command (Open Breaker) on page 7.43 for more information on the OPEN
command. Also, see Drive-to-Lockout and Drive-to-Last Shot Settings
(79DTL and 79DLS, Respectively) on page 4.146.
Reclosing Relay States and Settings/Setting Group Changes
If individual settings are changed for the active setting group or the active set-
ting 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).
If the relay happened to be in the Reclose Cycle State and was timing on an
open interval before the settings change, the relay would be in the Reclose
Cycle State after the settings change, but the relay would immediately go to
the lockout state. This is because the breaker is open, and the relay is at last
shot after the settings change, and thus no more automatic reclosures are
available.
If the circuit breaker remains closed through the settings change, the reset
timer times out on reset time setting 79RSLD after the settings change and
goes to the Reset State (if it is not already in the Reset State), and the shot
counter returns to shot = 0. If the relay happens to trip during this reset timing,
the relay immediately goes to the lockout state, because shot = last shot.
Defeat the Reclosing Relay
If any one of the following reclosing relay settings are made then the reclosing
relay is defeated, and no automatic reclosing can occur.
➤ Reclose enable setting E79 := N.
➤ Open Interval 1 time setting 79OI1 := 0.00.
If the reclosing relay is defeated, the following also occur:
➤ All three reclosing relay state Relay Word bits (79RS, 79CY,
and 79LO) are forced to logical 0 (see Tabl e 4.53).
➤ All shot counter Relay Word bits (SH0, SH1, SH2, SH3, and
SH4) are forced to logical 0 (the shot counter is explained later
in this section).
➤ The front-panel LEDs RECL RESET and RECL LOCKOUT are both
extinguished.
Close Logic Can Still Operate When the Reclosing Relay Is Defeated
If the reclosing relay is defeated, the close logic (see Figure 4.80) can still
operate if SEL
OGIC control equation circuit breaker status setting 52A is set to
something other than numeral 0 or NA. Making the setting 52A := 0 or NA
defeats the close logic and also defeats the reclosing relay.
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