Schweitzer Engineering Laboratories SEL-311L, Instruction Manual, Page: 496 / 734

11-10 Front-Panel Interface Date Code 20010625
SEL-311L Instruction Manual
Because this is an OFF/MOMENTARY type switch, the MANUAL TRIP switch returns to the
RETURN position after momentarily being in the TRIP position. Technically, the MANUAL
TRIP switch (being an OFF/MOMENTARY type switch) is in the TRIP position for one
processing interval (1/4 cycle; long enough to assert the corresponding local bit LB3 to logical 1)
and then returns to the RETURN position (local bit LB3 deasserts to logical 0 again).
On the display, the MANUAL TRIP switch is shown to be in the TRIP position for 2 seconds
(long enough to be seen), and then it returns to the RETURN position:
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The MANUAL CLOSE switch is an OFF/MOMENTARY type switch, like the MANUAL TRIP
switch, and operates similarly.
See Local Control Switches in Section 7: Inputs, Outputs, Timers, and Other Control Logic
for details on how local bit outputs LB3 and LB4 are set in SEL
OGIC
control equation settings to
respectively trip and close a circuit breaker.
Local Control State Retained When Relay Deenergized
Local bit states are stored in nonvolatile memory, so when power to the relay is turned off, the
local bit states are retained.
For example, suppose the local control switch with local bit output LB1 is configured as an
ON/OFF type switch (see Figure 11.5). Additionally, suppose it is used to enable/disable
reclosing. If local bit LB1 is at logical 1, reclosing is enabled:
If power to the relay is turned off and then turned on again, local bit LB1 remains at logical 1,
and reclosing is still enabled. This is similar to a traditional panel, where enabling/disabling of
reclosing and other functions is accomplished by panel-mounted switches. If dc control voltage
to the panel is lost and then restored again, the switch positions are still in place. If the reclosing
switch is in the enable position (switch closed) before the power outage, it will be in the same
position after the outage when power is restored.