Basler Electric BE1-851 - Manual (Page 166)

When used to provide high-speed overcurrent protection for the substation bus, it is recommended that all
51 function timing curves be set for instantaneous reset.
Normal Operation - Alarms
Two alarm logic variables drive the front panel alarm LEDs: Major alarm (ALMMAJ) and Minor alarm
(ALMMIN). ALMMAJ is set to drive the fail-safe output OUTA. ALMMIN is not set to drive an output relay.
The logic can be modified to place ALMMIN in the BESTlogic expression for VOA if all alarms are to be
combined. ALMMIN can be placed in the BESTlogic expression for another output if it is desired that
these conditions be enunciated separately.
Contingency Operation - Test Mode
The test mode is intended to increase the security of the feeder protection system if external test switches
are not installed on all outputs. When the relay is out of service for testing, the breaker failure and block
upstream instantaneous functions are disabled. Backup by the upstream relay is enabled and the
instantaneous function block trips are redirected to OUT1.
De-energizing IN4 will put the logic scheme in the test mode. IN4 can be controlled by a panel mounted
selector switch that is closed in the normal state and open in the test state. IN4 can also be controlled by
a pole of a standard external test switch that is opened with the rest of the test switch poles.
The logic expression for test mode drives Virtual Output 15 (VO15). This virtual output is alarm bit #23 in
the programmable alarm mask. It can be masked to drive an alarm LED to provide indication when the
relay is in test mode.
Contingency Operation - Backup Protection for Feeder Breaker Failure
OUT5 is programmed 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% of nominal.
Setting the time delay at zero can disable the BF function block. This permits the traditional radial
systems backup scheme of coordinated relays tripping different breakers.
Feeder_1 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
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 where the outputs are 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 8-5. Feeder_1 Contact Sensing Input Logic
Input Purpose Name Label
State Labels
Energized De-Energized
IN1 52b Breaker Status. BREAKER OPEN CLOSED
8-10 BE1-851 Application 9289900990 Rev R