Sel 411L - Figure 3.165 Current-Supervised Single-Pole Retrip Logic; Figure 3.166 no Current;Residual Current Circuit Breaker Failure Protection Logic Diagram

P.3.251
Date Code 20151029 Protection Manual SEL-411L Relay
Protection Functions
Circuit Breaker Failure Protection
Figure 3.165 Current-Supervised Single-Pole Retrip Logic
Circuit Breaker
Failure Initiation
Dropout and Seal-In
The relay circuit breaker failure protection features breaker failure initiation
extension and a breaker failure seal-in latch. The lower portion of
Figure 3.167 shows the dropout and seal-in logic.
Dropout Delay
Set timer BFIDO1 (breaker failure initiate dropout delay—BK1) to stretch a
short pulsed circuit breaker failure initiation. Use this feature for protecting
dual circuit breakers when separate 86 BF lockout relays have differing
energizing times.
Seal-In Delay
Set timer BFISP1 (breaker failure initiate seal-in delay—BK1) to qualify
extended circuit breaker failure initiation latch seal-in. When you set BFISP1
longer than BFIDO1 and the circuit breaker failure initiate is greater than the
difference of the two timers, the relay seals in the circuit breaker failure
extended initiation after the initiate signal deasserts until the BFIDO1 time
expires and all 50Fn elements deassert.
No Current/Residual
Current Circuit
Breaker Failure
Protection Logic
The relay has separate circuit breaker failure logic that operates on zero-
sequence current rather than phase current. Use this logic to detect a circuit
breaker failure and take appropriate action when a weak source drives the fault
or if the protected circuit breaker fails to trip during a high-resistance ground
fault. The residual current input to this logic is the 50R1 residual overcurrent
element (see Figure 3.166). Setting 50RP1 (residual current pickup—BK1) is
the pickup threshold setting for the 50R1 element.
Figure 3.166 No Current/Residual Current Circuit Breaker Failure Protection
Logic Diagram
Relay Word bit NBF1 (Breaker 1 low current breaker failure) asserts when
timer NPU1 (low current breaker failure time delay on pickup) expires and
one of the following conditions exists.
➤ Circuit Breaker 1 residual overcurrent element 50R1 is asserted
and the relay does not detect an open pole in any of the three
phases for Circuit Breaker 1 (i.e., NOT B1OPHA, NOT
B1OPHB, or NOT B1OPHC).
➤ Relay Word bit BFIN1 (no current breaker failure initiation) is
asserted.
BFIA1
BFIB1
BFIC1
RTA1
50FA1
RTSA1
Relay
Word
Bit
Relay
Word
Bits
SELOGIC
Settings
RTPU1
0
2 of 3
50R1
B1OPHA
B1OPHB
B1OPHC
BFI3P1
BFIN1
ENCBF1 := Y
NBF1
Relay
Word
Bits
Relay
Word
Bit
SELOGIC
Settings
Setting
NPU1
0