4.52
SEL-751A Relay Instruction Manual Date Code 20100129
Protection and Logic Functions
Trip/Close Logic
NOTE: You can use an indirect
mapping (e.g., SV01) as in the factory
default setting. See Ta bl e 4.35 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 required Relay Word bits.
REMTRIP Remote Trip Conditions SELOGIC Control Equation
You can map any Relay Word bit or SELOGIC equation to the REMTRIP to
trip the breaker. For example, you can map a control input to REMTRIP. Add
REMTRIP to the TR SEL
OGIC 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 any of the following
conditions 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 Breaker Status Conditions SELOGIC Control Equation
You can connect an auxiliary contact of the breaker to the relay. The SELOGIC
control equation 52A allows you to configure the relay for either 52b or 52a
contact input (or other contact that indicates a closed breaker). The factory
default setting assumes no auxiliary contact connection (52A := 0).
If you connect the breaker auxiliary contact to a digital input, you must change
the factory default logic equation 52A. For example, set 52A := IN101 if you
connect the 52a contact to input IN101.
Figure 4.30 shows the breaker close logic.
NOTE: The close logic is inoperative
if 52A is set to 0 in SEL-751A models
with reclosing option.
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