Date Code 20011205
Inputs, Outputs, Timers, and Other Control Logic
7-9
SEL-311A Instruction Manual
Local bit LB4 is set to close the circuit breaker in the following SEL
OGIC
control equation
setting:
CL = … + LB4 + …
SEL
OGIC
control equation setting CL is for close conditions, other than serial port
CLOSE
command (see Figure 6.1 in
Section 6: Close Logic
).
Additional Local Control Switch Application Ideas
Local control switches can be applied to almost any control scheme that traditionally requires
front-panel switches. The preceding settings examples are OFF/MOMENTARY switches. Local
control switches configured as ON/OFF switches can be used for such applications as ground
relay enable/disable or remote control supervision.
Local Control Switch States Retained
Power Loss
The states of the local bits (Relay Word bits LB1 through LB16) are retained if power to the
relay is lost and then restored. If a local control switch is in the ON position (corresponding
local bit is asserted to logical 1) when power is lost, it comes back in the ON position
(corresponding local bit is still asserted to logical 1) when power is restored. If a local control
switch is in the OFF position (corresponding local bit is deasserted to logical 0) when power is
lost, it comes back in the OFF position (corresponding local bit is still deasserted to logical 0)
when power is restored. This feature makes the local bit feature behave the same as a traditional
installation with panel-mounted control switches. If power is lost to the panel, the front-panel
control switch positions remain unchanged.
Settings Change or Active Setting Group Change
If settings are changed (for the active setting group or one of the other setting groups) or the
active setting group is changed, the states of the local bits (Relay Word bits LB1 through LB16)
are retained, much like in the preceding
Power Loss
explanation.
If settings are changed for a setting group other than the active setting group, there is no
interruption of the local bits (the relay is not momentarily disabled).
If a local control switch is made inoperable because of a settings change (i.e., the corresponding
label settings are nulled), the corresponding local bit is then fixed at logical 0, regardless of the
local bit state before the settings change. If a local control switch is made newly operable
because of a settings change (i.e., the corresponding label settings are set), the corresponding
local bit starts out at logical 0.
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