4.131
Date Code 20170927 Instruction Manual SEL-751 Relay
Protection and Logic Functions
Group Settings (SET Command)
If you connect the breaker auxiliary contacts to digital inputs, you must
change the factory-default logic equations for 52A and 52B. For example, set
52A := IN101 and 52B := IN102 if you connect the 52a and 52b contacts to
inputs IN101 and IN102, respectively.
The SEL-751 Relay with the touchscreen display option additionally provides
the ability to design detailed single-line diagrams and display the breaker and
disconnect switch status. Refer to Table 9.1 for typical circuit breaker symbols
available for display on the bay screens. For settings related to bay control
breaker symbols, refer to Table 9.5 and the corresponding description.
CL Close SELOGIC Control Equation
The SEL-751 Close Logic offers three ways to close the circuit breaker:
➤ Conditions mapped to CL
➤ Front-panel or serial port (including Modbus and DeviceNet)
CLOSE command
➤ Automatic reclosing when open interval times out (qualified by
SEL
OGIC control equation setting 79CLS—see Figure 4.81).
The relay controls the closing output contact(s) when the Relay Word bit
CLOSE appears in an output contact SEL
OGIC control equation. Default relay
settings have output OUT102 set to CLOSE. See Figure 2.23 for typical close
circuit connection.
Set the CL SEL
OGIC control equation to include an OR-combination of all
Relay Word bits that you want to cause the relay to close breaker. The factory-
default setting already includes all commonly necessary Relay Word bits.
Unlatch Close Logic
Once the CLOSE bit is asserted it is sealed-in until any of the following condi-
tions are true:
➤ Unlatch Close SELOGIC control equation setting ULCL asserts
to logical 1.
➤ Relay Word 52A asserts to logical 1.
➤ Close failure Relay Word bit asserts to logical 1.
Close Failure Logic
Set the close failure delay (setting CFD) equal to highest breaker close time
plus a safety margin. If the breaker fails to close, the Relay Word CF asserts
for 1/4 cycle. Use the CF bit as desired.
Reclose Supervision
Logic
Note that one of the inputs into the close logic in Figure 4.80 is:
Reclosing Relay Open Interval Time-Out (qualified by 79CLS)
This input into the close logic in Figure 4.80 is the indication that a reclosing
relay open interval has timed out (see Figure 4.82), a qualifying condition
(SEL
OGIC control equation setting 79CLS) has been met, and thus automatic
reclosing of the circuit breaker should proceed by asserting the CLOSE Relay
Word bit to logical 1. This input into the close logic in Figure 4.80 is an output
of the reclose supervision logic in the following Figure 4.81.
NOTE: For the settings related to
the local/remote breaker control
function, refer to Local/Remote
Breaker Control on page 9.3. For
breaker control via the front panel
pushbuttons, refer to Front-Panel
Operator Control Pushbuttons on
page 8.15. For breaker control via the
two-line display, refer to Control
Menu on page 8.9. For breaker
control via the touchscreen, refer to
Breaker Control Via the Touchscreen
on page 9.5.
NOTE: The close logic is inoperative
if 52A is set to 0 in SEL-751 models
with reclosing option.
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