BE1-951
BESTlogic Programmable Logic
7-5
Figure 7-3. Virtual Output Logic
25 VM2
25VM2 Sync Check voltage Monitor
150TQT
Negative Sequence Tripped
27PT
27 Phase Undervoltage Tripped
150TQPU
150T Negative Sequence Picked Up
27PPU
27 Phase Undervoltage Picked Up
Function Block Logic Settings
Each BESTlogic function block is equivalent to its discrete device counterpart. For example, the Reclosing
Logic Function Block of Figure 7-2 has many of the characteristics of a BE1-79M Multiple Shot Reclosing
Relay.
Before using a protection or control function block, two items must be set: the Mode and the Input Logic.
Setting the Mode is equivalent to deciding which protection or control functions will be used in a logic
scheme. The Input Logic establishes control of a function block.
Mode and input logic information is contained in logic setting command strings. Depending on the command,
the mode setting can either enable or disable a logic input or determine how a function block operates. Input
logic defines which logic variables control or disable a logic function. An example of an input logic equation
is SL-181=1,IN3+VO6. In this frequency logic command string, the 1 parameter indicates that the 181
function is enabled. The IN3+VO6 expression indicates that the 181 function is disabled when input 3 or
virtual output 6 are TRUE.
The AND operator may not be applied to the terms of an input logic equation. Any number of variables or
their inverse can be combined in a function block input logic expression. Section 4,
Protection and Control
provides detailed information about setting the logic for each function block.
Output Logic Settings
Defining Output Operation
Output operation is defined by Boolean logic equations. Each
variable in an equation corresponds to the current state
(evaluated every quarter cycle) of an input, output, or timer.
Figure 7-3 illustrates this relationship. Every quarter cycle, output
expressions are evaluated as TRUE or FALSE. If a logic output
that corresponds to a hardware output changes state, then the
corresponding output relay contact also changes state.
When the relay is powered up, all logic outputs are disabled and most variables (including virtual outputs)
initialize as FALSE. Some variable states are stored in EEPROM and are restored to the last state prior to
loss of power. These variables include 43/143/243/343,101SC, and SG0 through SG3. All control
commands, including logic override control, are also stored in EEPROM. If you override output logic and
force an output to open, that condition will be maintained even if operating power is cycled.
When the logic is running and logic expression SL-VO[n] is FALSE, then output VO[n] = 0. When the logic
is running and logic expression SL-VO[n] is TRUE, then VO[n] = 1. Hardware outputs OUTA and OUT1
through OUT5 follow the corresponding logic outputs VOA and VO1 through VO6.
Logic equations are defined by logic variables, logic operators, and their position in an equation. The
available logic operators include AND (
W
), OR (+), and NOT (/). The NOT operator is applied to the variable
immediately following the symbol (/). For virtual output equations, OR logic can be applied to any number
of variables if no AND logic is used in the expression. Similarly, AND logic can be applied to any number
of variables if no OR logic is used. Any number of NOT operators may be used. For complex expressions
that use both AND and OR operators, OR logic is limited to four terms. Up to four AND terms with any
number of variables can be ORed together. When the relay is processing a complex expression, it performs
AND operations before performing OR operations.
Logic expressions for virtual outputs are entered with the SL-VO (settings logic, virtual outputs) command.
SL-VO Command
Purpose:
Programs a logical mode of operation for a virtual output.
Syntax:
SL-VO<x>[=<equation>]
