Sel SEL-421 - Circuit Breaker Failure Protection; Trip a Unlatch Logic; Trip During Open Pole

R.1.115
Date Code 20111215 Reference Manual SEL-421 Relay
Protection Functions
Circuit Breaker Failure Protection
Figure 1.70 Trip A Unlatch Logic
Figure 1.71 Trip During Open Pole
Circuit Breaker Failure Protection
Use the SEL-421 to provide circuit breaker failure protection for as many as
two circuit breakers. The circuit breaker failure protection logic includes the
following schemes:
➤ Failure to interrupt fault current for phase currents
➤ Failure to interrupt load current
➤ No current/residual current circuit breaker failure protection
➤ Flashover protection while the circuit breaker is open
All schemes can incorporate single-pole and three-pole retrip. Single-pole and
three-pole initiations are available for circuit breaker failure, including
extended breaker failure initiation. The circuit breaker failure logic also
includes breaker failure trip latching logic.
The failure-to-interrupt-fault-current logic includes two schemes; both are
suitable for three-pole or single-pole tripping applications. Scheme 1 is basic
circuit breaker failure that is useful for most applications. Scheme 2 allows
0
1
CYC
3PT
LOPHA
TULO := 1
TULO := 2
52AA1
52AA2
TULO := 3
LOPHA
LOPHB
LOPHC
ULTRA
TULO := 4 Do not run this logic. ULTRA=0, ULTRB=0, ULTRC=0
Relay
Word
Bit
Relay
Word
Bit
Relay
Word
Bit
Relay
Word
Bits
Setting
Setting
Setting
NUMBK=2
1/8 CYC
TOPD
0
1/8
CYC
Relay
Word
Bit
Relay
Word
Bits
TOP
SPT
TPA
TPB
TPC
E3PT
SELOGIC
Setting