4.56
SEL-751A Relay Instruction Manual Date Code 20100129
Protection and Logic Functions
Reclose Supervision Logic
If 79CLS is asserted to logical 1 at the instant of an open interval time-out,
then the now-qualified open interval time-out will propagate onto the final
close logic in Figure 4.31 to automatically reclose the circuit breaker.
If 79CLS is deasserted to logical 0 at the instant of an open interval time-out,
the following occurs:
➤ No automatic reclosing takes place.
➤ Relay Word bit RCSF (Reclose Supervision Failure indication)
asserts to logical 1 for one processing interval.
➤ The reclosing relay is driven to Lockout State.
See Settings Example 1 on page 4.57.
For A Few, Unique Applications (Bottom of Figure 4.31 and Figure 4.32)
For a few unique applications, the Reclose Supervision Limit Time setting is
not set equal to zero seconds, e.g.,
79CLSD := 1.00 second
With this setting, the logic in the bottom of Figure 4.31 is operative. When an
open interval times out, the SEL
OGIC control equation reclose supervision
setting 79CLS is then checked for a time window equal to setting 79CLSD.
If 79CLS asserts to logical 1 at any time during this 79CLSD time window,
then the now-qualified open interval time-out will propagate onto the final
close logic in Figure 4.30 to automatically reclose the circuit breaker.
If 79CLS remains deasserted to logical 0 during this entire 79CLSD time
window, when the time window times out, the following occurs:
➤ No automatic reclosing takes place.
➤ Relay Word bit RCSF (Reclose Supervision Failure indication)
asserts to logical 1 for one processing interval.
➤ The reclosing relay is driven to Lockout State.
The logic in the bottom of Figure 4.31 is explained in more detail in the
following text.
Set Reclose Supervision Logic (Bottom of Figure 4.31)
Refer to the bottom of Figure 4.31. If all the following are true:
➤ The close logic output CLOSE (also see Figure 4.30) 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 in Figure 4.31. Then, when
79CLS asserts to logical 1, the sealed-in reclosing relay open interval time-out
condition will propagate through Figure 4.27 and on to the close logic in
Figure 4.30.
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