Basler Electric BE1-851 - Manual (Page 175)

Contingency Operation - Backup Protection for Feeder Breaker Failure
OUT5 is configured as the breaker failure trip output. OUT5 can be wired to trip the bus breaker or a
lockout relay. The breaker failure pickup (BFPU) output trips the feeder breaker directly via output 1 to
provide a breaker re-trip signal for added security.
Initiation of the BF function block by external relays is not accommodated in this scheme. IN2, IN3, or IN4
can be programmed to provide this function or Feeder_4 logic may be used. The breaker failure function
block is initiated by a protective trip. This function block has an independent fast drop out phase and
ground current detector that detects a breaker opening and stops timing. An open breaker is detected
when the current drops below 10 percent of nominal.
Setting the time delay at zero disables the BF function block. This permits the traditional radial system
backup scheme of coordinated relays tripping different breakers.
Feeder_2 logic stops the block signal to allow the bus relay to trip the bus breaker through its 50T
elements if a direct trip is not desired. This provides clearing of the fault on the circuit with the failed
breaker in feeder relay breaker time (or bus relay 50T time; whichever is greater) instead of the bus relay
51 time but is limited by the sensitivity constraints of the bus relay.
Contingency Operation - Backup Protection for Feeder Relay Out-of-Service
When the relay is out of service or it has failed, OUT3 opens to signal the upstream relays providing
backup protection. OUT3 operates in a fail-safe mode; the output is closed during normal operation and
open during a relay failure. This provides backup mode signaling when the feeder relay is extracted from
the case.
Backup for relay failure can be implemented using the BUS and BACKUP preprogrammed logic schemes.
These logic schemes are described later in this section.
Table 8-9. Feeder_2 Contact Sensing Input Logic
Input Purpose Name Label
State Labels
Energized De-Energized
IN1 52b Breaker Status. BREAKER OPEN CLOSED
IN2 Enable recloser when IN2 is energized. RCL_ENABLE ENABLED DISABLD
IN3
Enable neutral and negative-sequence,
50 and 51 protection when IN3 is
energized.
N&Q_ENABLE ENABLED DISABLD
IN4
Put the relay in test mode so that
reclosing and breaker failure are
disabled when IN4 is de-energized.
TESTDISABL NORMAL TSTMODE
Table 8-10. Feeder_2 Function Block Logic
Function Purpose
BESTlogic
Expression
Mode
Setting
50TP
Used for instantaneous phase overcurrent protection.
Block when recloser sequence controlled blocking
output is TRUE.
79SCB 1 (enabled)
50TN
Used for instantaneous neutral overcurrent protection.
Block when recloser sequence controlled blocking
output is TRUE or when disabled by IN3 or Virtual
Switch 243.
79SCB+/IN3+243 1 (enabled)
9289900990 Rev R BE1-851 Application 8-19