7-32
Inputs, Outputs, Timers, and Other Control Logic
Date Code 20020215
SEL-351R Instruction Manual
Timer pickup setting SV7PU provides breaker failure timing. Timer dropout setting SV7DO
holds the breaker failure trip output (output contact OUT102) closed for extra time if needed
after the breaker failure logic unlatches (fault detectors 50P1 and 50N1 dropout).
Note that Figure 7.25 suggests the option of having output contacts OUT103 and OUT104
operate as additional breaker failure trip outputs. This is done by making the following SEL
OGIC
control equation settings:
OUT103 = SV7T
(breaker failure trip)
OUT104 = SV7T
(breaker failure trip)
Settings Example 3
The seal-in logic circuit in the dedicated breaker failure scheme in Figure 7.25 can be removed
by changing the SEL
OGIC
control equation setting SV7 to:
SV7 = IN101 * (50P1 + 50N1)
If the seal-in logic circuit is removed, optoisolated input IN101 (breaker failure initiate) has to be
continually asserted for a breaker failure time-out.
Timers Reset When Power Is Lost, Settings Are Changed, or Active Setting Group Is
Changed
If power is lost to the relay, settings are changed (for the active setting group), or the active
setting group is changed, then the SEL
OGIC
control equation variables/timers are reset. Relay
Word bits SVn and SVnT (n = 1 through 16) are reset to logical 0 and corresponding timer
settings SVnPU and SVnDO load up again after power restoration, settings change, or active
setting group switch.
Preceding Figure 7.25 shows an effective seal-in logic circuit, created by use of Relay Word bit
SV7 (SEL
OGIC
control equation variable SV7) in SEL
OGIC
control equation SV7:
SV7 = (SV7 + IN101) * (50P1 + 50N1)
If power is lost to the relay, settings are changed (for the active setting group), or the active
setting group is changed, then the seal-in logic circuit is “broken” by virtue of Relay Word bit
SV7 being reset to logical 0 (assuming input IN101 is not asserted). Relay Word bit SV7T is
also reset to logical 0, and timer settings SV7PU and SV7DO load up again.
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