Schweitzer Engineering Laboratories SEL-311L, Instruction Manual, Page: 283 / 734

Date Code 20010625 Inputs, Outputs, Timers, and Other Control Logic 7-31
SEL-311L Instruction Manual
Additional Settings Example 1
Another application idea is dedicated breaker failure protection (see Figure 7.25):
SV6 = IN101 (breaker failure initiate)
SV7 = (SV7 + IN101) * (50P1 + 50G1)
OUT101 = SV6T (retrip)
OUT102 = SV7T (breaker failure trip)
Figure 7.25: Dedicated Breaker Failure Scheme Created With SEL
OGIC
Control Equation
Variables/Timers
Note that the above SEL
OGIC
control equation setting SV7 creates a seal-in logic circuit (as
shown in Figure 7.25) by virtue of SEL
OGIC
control equation setting SV7 being set equal to
Relay Word bit SV7 (SEL
OGIC
control equation variable SV7):
SV7 = (SV7 + IN101) * (50P1 + 50G1)
Optoisolated input IN101 functions as a breaker failure initiate input. Phase instantaneous
overcurrent element 50P1 and residual ground instantaneous overcurrent element 50G1 function
as fault detectors.
Timer pickup setting SV6PU provides retrip delay, if desired (can be set to zero). Timer dropout
setting SV6DO holds the retrip output (output contact OUT101) closed for extra time if needed
after the breaker failure initiate signal (IN101) goes away.
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 50G1 dropout).