5-6 Applications Date Code 20000421
SEL-251, -2, -3 Instruction Manual
Using SELOGIC Control Equations:
S(123)N = 50C
Figure 5.5: 50C Delayed by TSPU Time
If 50L is supervised by ST, 50L continues to be disabled for time period TSPU after the circuit
breaker closes and load is picked up. Set TSPU slightly greater than the potential cold load
inrush time.
Continuing with SELOGIC Control Equations:
B(12) = 50L
E(34) = ST (time delayed 50C)
V(56) = B*E
TR(1246) = V+... (TR is the programmable trip condition)
effectively, TR(1246) = 50L*ST+...
close TRIP output contacts = TR + ...
If the TSDO setting exceeds the longest reclosing relay open interval time setting (79OI1, 79OI2,
etc.), ST will not drop out during the reclose cycle. Thus, 50L remains enabled throughout the
cycle. ST drops out when TSDO expires after the recloser goes to lockout (the circuit breaker is
open and 50C = 0). This may be desirable since typical open interval times are not long enough
to warrant concern about cold load inrush. Thus, 50L is disabled for TSPU time only after the
circuit breaker closes from the lockout state.
To disable 50L only after the circuit breaker closes from the lockout state, make the following
settings.
Using SELOGIC Control Equations:
S(123) = 50C
B(12) = 50L
E(34) = 79RS+79CY+ST
V(56) = B*E
TR(1246) = V+... (TR is the programmable trip condition)
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