Basler Electric BE1-851 - Manual (Page 193)

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 provided by IN3. The 150T function blocks provide
fault detector supervision of the external initiate signal. The logic uses the pickup outputs of the function
blocks. In this application, the time delay settings should be set to maximum so that they do not time out
and trip targets. If the external BFI signal from protective relays such as 81 or 87T where fault detector
supervision is not desired, the BESTlogic expression for VO12 which is the BFI logic expression in this
logic scheme, can be modified.
The BF function block is also 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% 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_4 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 failure 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
Primary protection for relay failure is provided by redundant relays applied to the feeder.
Table 8-17. Feeder_4 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 8-18. Feeder_4 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 Virtual Switch
243.
79SCB+243 1 (enabled)
9289900990 Rev R BE1-851 Application 8-37