R.3.32
SEL-421 Relay Reference Manual Date Code 20111215
SELOGIC Control Equation Programming
SELOGIC Control Equation Operators
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 negative 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 on page R.3.30. EXP calculates the value of e raised to
the power of the argument. Example 3.16 shows examples of expressions that
use the LN, EXP, and LOG operators.
EXAMPLE 3.16 Using the LN, EXP, and LOG Operators
The free-form math SEL
OGIC 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
# EXP examples
AMV004 := EXP (2) # Calculates e squared
AMV005 := EXP (AMV003) # Calculates e to the power AMV003
AMV006 := EXP (AMV046 + AMV047) # e raised to the power of the sum
# LOG examples
AMV007 := LOG (AMV012) # Base 10 logarithm of AMV012
AMV008 := LOG (AMV012 + AMV022) # Base 10 logarithm of the sum
AMV009 := LOG (AMV100) # Produces an error if AMV100 is 0 or negative
SIN and COS
Use the SIN or COS operators to calculate the sine or cosine of the argument.
SIN and COS operate in degrees, the unit of angular measure the SEL-421
uses to express metering quantities. Example 3.17 shows examples of SIN and
COS.
EXAMPLE 3.17 Using the SIN and COS Operators
The free-form math SEL
OGIC control equations below are examples of
SIN and COS.
# SIN examples
AMV001 := SIN (AMV005) # Sine of AMV005
AMV002 := SIN (AMV005 + AMV034) # Sine of the sum
# COS examples
AMV003 := COS (AMV005) # Cosine of AMV005
AMV004 := COS (AMV005 + AMV006) # Cosine of the sum
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