4-76 BE1-951 Protection and Control 9328900990 Rev L
VIRTUAL SWITCHES
43 - Virtual Selector Switches
BE1-951 relays have four virtual selector switches that can provide manual control, locally and remotely,
without using physical switches and/or interposing relays. Each virtual switch can be set for one of three
modes of operation to emulate virtually any type of binary (two position) switch. An example would be an
application that requires a recloser or 51N ground cutoff. The traditional approach might be to install a
switch on the panel and wire the output to a contact sensing input on the relay. Instead, a virtual switch
can be used to reduce costs with the added benefit of being able to operate the switch both locally
through the HMI and remotely from a substation computer or through a modem connection to a remote
operator’s console.
The state of the switches can be controlled from the HMI or ASCII command interface. The BESTlogic
mode setting can set control actions. When set for the On/Off/Pulse mode, each switch can be controlled
to open (logic 0), close (logic 1), or pulse such that the output toggles from its current state to the
opposite state and then returns. Additional modes allow the switch operation to be restricted. In the
On/Off mode, the switch emulates a two-position selector switch, and only open and close commands are
accepted. In the Off/Momentary On mode, a momentary close, spring return switch is emulated and only
the pulse command is accepted. Because switch status information is saved in nonvolatile memory, the
relay powers up with the switches in the same state as when the relay was powered down.
Each virtual selector switch function block (see
Figure 4-71) has one output: 43, 143, 243, or 343. The
output is TRUE when the switch is in the closed state; the output is FALSE when the switch is in the open
state. Since both the output and the inverse of the output of these switches can be used as many times
as desired in your programmable logic, they can emulate a switch with as many normally open and
normally closed decks as desired.
43
Mode
0-Disable
1-On/Off/Pulse
2-On/Off
3-Off/Momentary On
43 AUX
SWITCH
D2861-05
03-13-00
Figure 4-71. Virtual Selector Switches Logic Block
User specified labels could be assigned to each virtual switch and to both states of each switch. In the
previous differential cutoff switch example, you might enable one of the switches in BESTlogic as On/Off
and connect the output of that switch to the Block input of the 51P protection element block. This would
disable the differential when the switch is closed (logic 1) and enable it when the switch is open (logic 0).
For the application, you might set the switch label to be 51_CUTOFF (10 character maximum). The
closed position on the switch might be labeled DISABLD (7 character maximum) and the open position
might be labeled NORMAL. Section 7, BESTlogic Programmable Logic, has more details about setting
user programmable names for programmable logic variables.
BESTlogic Settings for Virtual Selector Switches
BESTlogic settings are made from the BESTlogic Function Element screen in BESTCOMS.
Figure 4-72
illustrates the BESTCOMS screen used to select BESTlogic setting for the Virtual Switch element. To
open the BESTlogic Function Element screen for Virtual Switch, select Virtual Switches from the S
creens
pull-down menu. Then select the BESTlogic button for the 43, 143, 243, or 343 element. Alternately,
settings may be made using SL-<x>43 ASCII command.
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