7.8
SEL-351A Relay Instruction Manual Date Code 20080213
Inputs, Outputs, Timers, and Other Control Logic
Local Control Switches (Only on Models With LCD)
Additional Local
Control Switch
Application Ideas
The preceding factory settings examples are OFF/MOMENTARY switches.
Local control switches configured as ON/OFF switches can be used for such
applications as:
➤ Reclosing relay enable/disable
➤ Ground relay enable/disable
➤ Remote control supervision
➤ Sequence coordination enable/disable
Local control switches can also be configured as ON/OFF/MOMENTARY
switches for applications that require such. Local control switches can be
applied to almost any control scheme that traditionally requires front-panel
switches.
Local Control Switch
States Retained
Power Loss
The states of the local bits (Relay Word bits LB1–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.
If a local bit is routed to a programmable output contact and control power is
lost, the state of the local bit is stored in nonvolatile memory but the output
contact will go to its de-energized state. When the control power is applied
back to the relay, the programmed output contact will go back to the state of
the local bit after relay initialization.
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–LB16) are retained, much like in the 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.
Courtesy of NationalSwitchgear.com
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