4.22
SEL-400 Series Relays Instruction Manual Date Code 20171006
Front-Panel Operations
Front-Panel Menus and Screens
Local Control Bits
The relay provides 32 local control bits with SELOGIC control equation supervi-
sion. These local bits replace substation control handles to perform switching
functions such as bus transfer switching. The relay saves the states of the local
bits in nonvolatile memory and restores the local bit states at relay power-up.
NOTE: The default settings for
LB_SPnn are “1”. The default settings
satisfy the local bit supervision logic
so that local bit operations can take
place.
Local control bit supervision is available through a SELOGIC control equation
provided in the Front Panel settings (LB_SPnn). For local bit operations to take
place, the corresponding LB_SPnn must be asserted. Table 4.8 defines the local
bit SEL
OGIC settings available in the Front Panel settings class. Figure 4.27 illus-
trates the logic that supervises all local bit operations (Set, Clear, Pulse).
NOTE: The default settings for
LB_DP
nn
are LB
nn
. The default
settings cause the local bit switch to
move to the corresponding state of
the local bit (asserted = 1,
deasserted = 0).
The SELOGIC control equation local bit status (LB_DPnn) is provided to return
the status of a device that is being controlled by the local bit. The LB_DPnn
Relay Word bit drives the state of the graphical switch on the display (i.e., with
LB_DPnn deasserted, the switch points to 0).
Any unused local control bits default to the clear (logical 0) state. Also, any
reconfigured local bit retains the existing bit state after you change the bit setting.
Deleting a local bit sets that bit to the clear (logical 0) state.
In the top part of Figure 4.26, the following custom labeled functions are those
controlled by local control bit operation.
➤ Enable Bus Switching
➤ North Bus MOD
➤ South bus MOD
➤ Bus Tie Interlock
➤ Alternate Settings 3
In addition, Figure 4.26 gives an example of a custom-labeled function, Bus Tie
Interlock. The LCD shows a graphic representation of a substation control han-
dle. The LB_DPnn SEL
OGIC control equation determines the state of the switch
position on the LCD. If the LB_DPnn Relay Word bit is deasserted, the graphic
control handle points to 0; if the LB_DPnn Relay Word bit is asserted, the switch
points to 1.
You can program names or aliases for the local bit clear and set states—these
appear next to logical 0 and logical 1, respectively, in the lower portion of the
sample Bus Tie Interlock screens of Figure 4.26. Use the Up Arrow and Down Arrow
pushbuttons to highlight the set (1) or clear (0) control actions. Highlighting the
set option (shown in Figure 4.26 as
Closed (OK to TIE)) and pressing ENT
changes the local control bit and performs the required control action. If the
LB_DPnn Relay Word bit asserts, the graphical switch moves to 1 to indicate the
asserted local bit status.
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