4.87
Date Code 20100129 Instruction Manual SEL-751A Relay
Protection and Logic Functions
Logic Settings (SET L Command)
Boolean Comparison Operators (<, >, <=, and >=)
Comparisons are mathematical operations that compare two numerical values,
with the result being a logical 0 (if the comparison is not true) or logical 1 (if
the comparison is true). Thus, what starts out as a mathematical comparison
ends up as a Boolean resultant. For example, if the output of a math variable is
above a certain value, an output contact is asserted:
OUT103 := MV01 > 8
If the math variable (MV01) is greater than 8 in value, output contact OUT103
asserts (OUT103 = logical 1). If the math variable (MV01) is less that or equal
to 8 in value, output contact OUT103 deasserts (OUT103 = logical 0).
Boolean Equality (=) and Inequality (<>) Operators
Equality and inequality operators operate similar to the comparison operators.
These are mathematical operations that compare two numerical values, with
the result being a logical 0 (if the comparison is not true), or logical 1 (if the
comparison is true). Thus, what starts out as a mathematical comparison, ends
up as a Boolean resultant. For example, if the output of a math variable is not
equal to a certain value, an output contact is asserted:
OUT102 := MV01 <> 45
If the math variable (MV01) is not equal to 45 in value, output contact
OUT102 asserts (effectively OUT102 := logical 1). If the math variable
(MV01) is equal to 45 in value, output contact OUT102 deasserts (effectively
OUT102 := logical 0). The following table shows other operators and values
that you can use in writing SEL
OGIC control equations.
Timers Reset When
Power Lost or
Settings Changed
If the device loses power or settings change, the SELOGIC control equation
variables/timers reset. Relay Word bits SVn and SVnT (n = 01–32) reset to
logical 0 after power restoration or a settings change. Figure 4.47 shows an
effective seal-in logic circuit, created by the use of Relay Word bit SV07
(SEL
OGIC control equation variable SV07) in SELOGIC control equation
SV07:
SV07 = (SV07 OR OUT101) AND (OUT102 OR OUT401)
Ta b le 4 . 3 4 O t h e r SEL OGIC Control Equation Operators/Values
Operator/
Value
Function
Function Type
(Boolean and/or
Mathematical)
0
Set SEL
OGIC control equation directly to logical 0
(XXX := 0)
Boolean
1
Set SEL
OGIC control equation directly to logical 1
(XXX := 1)
Boolean
#
Characters entered after the # operator are not
processed and deemed as comments
Boolean and
Mathematical
\
Indicates that the preceding logic should be
continued on the next line (“\” is entered only at the
end of a line)
Boolean and
Mathematical
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