4.130
SEL-751 Relay Instruction Manual Date Code 20170927
Protection and Logic Functions
Group Settings (SET Command)
The default TR setting is shown in Table 4. 5 2 and includes protective ele-
ments Relay Word bits, front panel or serial port (including Modbus and Devi-
ceNet) initiated OPEN command (Relay Word bit OC), and remote trips
(Relay Word bit REMTRIP).
The trip conditions trigger an event report. The relay controls the tripping out-
put contact(s) when the Relay Word bit TRIP appears in an output contact
SEL
OGIC control equation. Default relay settings have output OUT103 set to
TRIP and fail-safe setting OUT103FS at N (see Fail-Safe/Nonfail-Safe Tripping
on page 2.26).
NOTE: You can use an indirect
mapping (e.g., SV01) as in the factory-
default setting. See Table 4.62 for the
SV01 settings.
Set the TR SELOGIC control equation to include an OR combination of all the
Relay Word bits that you want to cause the relay to trip. The factory-default
setting already includes all commonly necessary Relay Word bits.
REMTRIP Remote Trip Conditions SELOGIC Control Equation
The REMTRIP SELOGIC control equation is intended to define a remote trip
condition. For example, the following settings trip the breaker by input IN303
via REMTRIP.
REMTRIP := IN303
TR := … OR REMTRIP
The HMI displays
Remote Trip to indicate the trip by Remote trip logic.
You can map any Relay Word bit or SEL
OGIC control equation to the REM-
TRIP to trip the breaker. For example, you can map a control input to REM-
TRIP. Add REMTRIP to the TR SEL
OGIC control equation (as in the default
settings) to quickly see from the HMI target that it was a
Remote Trip that
tripped the breaker.
Unlatch Trip Logic
Following a fault, the trip signal is maintained until all of the following condi-
tions are true:
NOTE: Factory default setting of the
ULTRIP provides an automatic reset of
the trip when breaker opens and
selected 50/51 elements are not
picked up.
➤ Minimum trip duration time (TDURD) passes.
➤ The TR SELOGIC control equation result deasserts to logical 0.
➤ One of the following occurs:
➢ Unlatch Trip SELOGIC control equation setting
ULTRIP asserts to logical 1.
➢ Target Reset SELOGIC control equation setting
RSTTRGT asserts to logical 1.
➢ Target Reset Relay Word TRGTR asserts. The TRGTR
is asserted when the front-panel TARGET RESET
pushbutton is pressed or a target reset serial port
command is executed (ASCII, Modbus, or DeviceNet).
52A and 52B Breaker Status SELOGIC Control Equations
Use the SELOGIC settings 52A and 52B to map the respective breaker auxil-
iary contacts to the relay. Because the 52B contact is not always available for
the purpose of reducing the number of I/O required, the breaker status logic
does not include the 52B contact. The relay uses the 52A Relay Word bit as
the status of the breaker in conjunction with the protection elements and trip
and close logic. The default 52B setting is NOT 52A. The factory-default set-
ting assumes no auxiliary contact connection (52A := 0).
NOTE: For the disconnect switch
settings and logic, refer to
Disconnect Switch Symbol Settings
and Status Logic. For the
touchscreen relay option, refer to
Table 9.3 for typical disconnect
switch symbols. For the settings
related to bay control disconnect
switch symbols, refer to Table 9.5 and
the corresponding descriptions.
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