13.31
Date Code 20171006 Instruction Manual SEL-400 Series Relays
SELOGIC Control Equation Programming
SEL
OGIC Control Equation Operators
SQRT
Use the SQRT operation to calculate the square root of the argument. Use paren-
theses to delimit the argument of a SQRT operation. A negative argument for the
SQRT operation results in a math error and assertion of the corresponding math
error bit described in Arithmetic. Example 13.14 shows examples of the SQRT
operator in use.
LN, EXP, and LOG
LN and EXP are complementary functions for operating with natural logarithms
or logarithms calculated to the natural base e. LN calculates the natural logarithm
of the argument. LOG calculates the base 10 logarithm of the argument. A nega-
tive or zero argument for the LN and LOG operation results in a math error and
assertion of the corresponding math error bit described in Arithmetic. EXP calcu-
lates the value of e raised to the power of the argument. Example 13.15 shows
examples of expressions that use the LN, EXP, and LOG operators. Use parenthe-
ses to delimit the argument of a LN, EXP, or LOG operation.
The lines below demonstrate math calculation error detection.
# The line below results in a math error if AMV029 becomes 0
AMV006 := 732 / AMV029
In the second line, if AMV029 is 6 on the first pass through the automation
programming, the relay stores the result 122 in AMV006. If on the next pass
AMV029 is 0, the MATHERR bit asserts and the value in AMV006 does not
update.
Example 13.13 Using Arithmetic Operations (Continued)
Example 13.14 Using the SQRT Operator
The freeform math SELOGIC control equations below show examples of
SQRT operator usage.
# SQRT examples
AMV001 := SQRT (AMV005) # Single argument version of SQRT
AMV002 := SQRT (AMV005 + AMV034) # Calculates the square root
of the sum
AMV003 := SQRT (AMV007) # Produces a math error if AMV007 is
negative
Example 13.15 Using the LN, EXP, and LOG Operators
The freeform math SELOGIC control equations below are examples of LN,
EXP, and LOG operator usage.
# LN examples
AMV001 := LN (AMV009) # Natural logarithm of AMV009
AMV002 := LN (AMV009 + AMV034) # Natural logarithm of the sum
AMV003 := LN (AMV010) # Produces error if AMV010 is 0 or negative
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