4.147
Date Code 20170927 Instruction Manual SEL-751 Relay
Protection and Logic Functions
Group Settings (SET Command)
Additionally, if the reclosing relay should go to the lockout state for an
underfrequency trip, make settings similar to the following:
79DTL := TRIP AND 81D1T OR …
Other Settings Considerations
If no special drive-to-lockout or drive-to-last shot conditions are desired, make
the following settings:
79DTL := 0 (numeral 0)
79DLS := 0 (numeral 0)
With settings 79DTL and 79DLS inoperative, the relay still goes to the lock-
out state (and to last shot) if an entire automatic reclose sequence is unsuc-
cessful.
Overall, settings 79DTL or 79DLS are necessary to take the relay to the lock-
out state (or to last shot) for immediate circumstances.
Skip Shot (79SKP) and Stall Open Interval Timing (79STL) Settings
The skip shot setting 79SKP causes the relay to skip a reclose shot. Thus, the
relay skips an open interval time and uses the next open interval time instead.
If 79SKP = logical 1 at the instant of successful reclose initiation (see preced-
ing discussion on settings 79RI and 79RIS), the relay increments the shot
counter to the next shot and then loads the open interval time corresponding to
the new shot (see Tabl e 4 .5 5). If the new shot is the “last shot,” no open inter-
val timing takes place, and the relay goes to the lockout state if the circuit
breaker is open (see Lockout State on page 4.139).
After successful reclose initiation, open interval timing does not start until allowed
by the stall open interval timing setting 79STL. If 79STL = logical 1, open interval
timing is stalled. If 79STL = logical 0, open interval timing can proceed.
If an open interval time has not yet started timing (79STL = logical 1 still), the
79SKP setting is still processed. In such conditions (open interval timing has
not yet started timing), if 79SKP = logical 1, the relay increments the shot
counter to the next shot and then loads the open interval time corresponding to
the new shot (see Table 4 .55). If the new shot turns out to be the “last shot,” no
open interval timing takes place, and the relay goes to the lockout state if the
circuit breaker is open (see Lockout State on page 4.139).
If the relay is in the middle of timing on an open interval and 79STL changes
state to 79STL = logical 1, open interval timing stops where it is. If 79STL
changes state back to 79STL = logical 0, open interval timing resumes where
it left off. Use the OPTMN Relay Word bit to monitor open interval timing
(see Monitoring Open Interval and Reset Timing on page 4.143).
EXAMPLE 4.23 Factory Settings Example
The skip shot function is not enabled in the factory settings:
79SKP := 0 (numeral 0)
The stall open interval timing factory setting is:
79STL := TRIP
After successful reclose initiation, open interval timing does not start as
long as the trip condition is present (Relay Word bit TRIP = logical 1). As
discussed previously, if an open interval time has not yet started timing
(79STL = logical 1 still), the 79SKP setting is still processed. Once the trip
condition goes away (Relay Word bit TRIP = logical 0), open interval timing
can proceed.
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