Basler Electric BE1-851 - Manual (Page 201)

interrupt the fault. These are set up to trip the 86B relay also via OUT4. If a bus fault lockout relay is not
used, OUT4 can be wired in parallel with OUT1 to direct trip the bus breaker.
The BUS and BACKUP 50T functions should be set with a higher pickup that the highest feeder
instantaneous elements to ensure that they will not pickup before any feeder relay.
If there is a contingency problem such as a relay removed from service, 51 protection is still provided. The
BUS and BACKUP 51 functions are enabled for tripping via OUT1. The 51 functions are not blocked to
allow clearing a bus fault with a traditional coordination interval. 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 - Setting Group Selection
For normal operation, the BUS and BACKUP relays are in setting group 0. In setting group 0, the two
relays will only trip the bus breaker. Input 2 to the BACKUP relay identifies when a feeder relay is out of
service. The BACKUP relay then closes OUT3 that is connected to input 3 of the BUS relay. The two
relays then switch to setting group 1. Setting group selection mode 2, binary coded selection, is used to
recognize the group setting state. When input D0 to the setting group selection function block is a 1, it is
interpreted as a binary 1 causing the logic to switch to group 1.
When the relay is in setting group 1, the relays are operating in feeder relay backup mode. This
expression is programmed to virtual output 13 of the BUS relay that drives alarm bit #21 in the
programmable alarm mask. It can be masked to drive an alarm LED and alarm display to indicate when
the BUS relay is in feeder backup mode and to trip a feeder breaker instead of the bus breaker.
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 protection and control system if external test
switches are not installed on all outputs. When the BUS relay is out of service for testing, the overcurrent
protection function trip outputs are routed to OUT1 only. When the BACKUP relay is out of service for
testing, the overcurrent protection function trip outputs are routed to OUT1 only and the breaker failure
function is disabled.
De-energizing IN4 or closing Virtual Switch 343 will put the logic in 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 and HMI alarm display to provide
indication when the relay is in test mode.
Contingency Operation - Backup Protection for Bus Breaker Failure
Bus breaker failure protection is provided by the main bus relay using preprogrammed logic scheme
BACKUP. OUT5 is configured as the breaker failure trip output. OUT5 can be wired to trip the upstream
breaker or a bus breaker failure lockout relay or other lockout relay that trips the transformer high side
such as the 86T transformer differential lockout relay.
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. If you are
tripping for a bus fault via a lockout relay, the additional time delay of the lockout relay should be added to
your breaker failure time setting.
9289900990 Rev R BE1-851 Application 8-45