Sel SEL-421 - Control Equation Operators; Operator Precedence; Boolean Operators; Operator Precedence from Highest to Lowest

R.3.25
Date Code 20111215 Reference Manual SEL-421 Relay
SELOGIC Control Equation Programming
SELOGIC Control Equation Operators
SELOGIC Control Equation Operators
There are two types of SELOGIC control equations. Boolean SELOGIC control
equations comprise the first type. These equations are expressions that
evaluate to a Boolean value of 0 or 1. Math SEL
OGIC control equations
constitute the second type. The relay evaluates these equations to yield a result
having a numerical value (for example, 6.25 or 1055).
Left value, LVALUE, determines the type of SEL
OGIC control equation you
need for a setting or for writing free-form programming. If the LVALUE is a
Boolean type (52AA1, ASV001, etc.) then the type of expression you need is
a Boolean SEL
OGIC control equation. If the LVALUE is a numerical (non-
Boolean) value (PMV12, PCT01PV, etc.), the type of expression you need is a
math SEL
OGIC control equation.
Writing SEL
OGIC control equations requires that you use the appropriate
operators and correct SEL
OGIC control equation syntax to combine relay
elements including analog values, Relay Word bits, incoming control points,
and SEL
OGIC control equation elements within the relay. The operators are
grouped into two types, according to the type of SEL
OGIC control equation in
which you can apply these operators.
Operator Precedence
When you combine several operators and operations within a single
expression, the SEL-421 evaluates the operations from left to right, starting
with the highest precedence operators working down to the lowest precedence.
This means that if you write an equation with three AND operators, for
example PSV01 AND PSV02 AND PSV03, each AND will be evaluated from
the left to the right. If you substitute NOT PSV04 for PSV03 to make PSV01
AND PSV02 AND NOT PSV04, the relay evaluates the NOT operation of
PSV04 first and uses the result in subsequent evaluation of the expression.
While you cannot use all operators in any single equation, the overall operator
precedence follows that shown in Table 3.19.
Boolean Operators
Use Boolean operators to combine values with a resulting Boolean value. The
arguments of the operator may be either numbers or Boolean values, but the
result of the operation must be a Boolean value. Combine the operators to
form statements that evaluate complex Boolean logic. Table 3.20 contains a
summary of Boolean operators available in the SEL-421.
Table 3.19 Operator Precedence from Highest to Lowest (Sheet 1 of 2)
Operator Description
(Expression) Parenthesis
Identifier (argument list) Function evaluation
–Negation
NOT Complement
R_TRIG
F_TRIG
Edge Trigger
SQRT, LN, EXP, LOG, COS, SIN, ACOS,
ASIN, ABS, CEIL, FLOOR
Math Functions
* Multiply
/Divide
+Add