GE D90 Plus Instruction Manual page 430

AUTOMATION LOGIC
About editing operators
422
Syntax Description
Return the natural logarithm (base e) value of the previous operand.
LOG
Return the base 10 logarithm value of the previous operand.
LOG10
Return magnitude of the previous two operands, where the first operand is
MAG (a, b)
the real value the second operand is the imaginary value.
Multiply the previous two operands.
MUL (a, b)
Multiply the previous operand by –1.
NEG
Raise the first operand to a power of the second operand.
POW (a, b)
Return real value of the previous two operands, where the first operand is
REAL (a, b)
the magnitude and the second operand is the angle.
Return the sine value of the previous operand.
SIN
Return the square root of the previous operand.
SQRT
Subtract the second operand from the first operand.
SUB (a ,b)
Return the tangent value of the previous operand.
TAN
The automation controller can perform math operations on any analog input, any
numerical constant, or the output of a preceding math operator. The final output of a
sequence of math operations is stored as a virtual analog output (VAO). Numerical
constants are IEEE 32-bit floating-point values and are fixed during operation of the
controller. The math operators available in the automation controller are tabulated below.
Any analog input or the result of any math operation can be assigned to a FlexElement™,
which is a general purpose analog comparator. A FlexElement™ compare a single input
with a threshold value or can compare two inputs. The output from a FlexElement™ can be
used for further logic processing. The number of FlexElements dedicated is 16.
All math calculations are carried out using 32-bit IEEE floating-point numbers as defined
by IEEE 754-185. This format has a range of –3.402823 × 10
Consider the following math calculation.
The automation logic for this example is shown below.
When using programming language, it is a best practice to initialize a variable before using
it within a program. The same principle applies to using virtual analog values in
automation logic. For example, if we desire an automation logic equation of the form AVO1
+ SRC 4 Ig RMS = AVO3, then the result of AVO3 depends of the previous value of the AVO1
(this can any value between –∞ and +∞). As a result, the AVO3 value will be indeterministic.
In this case, a better approach is to initialize virtual analog output 1 as follows.
AVO1 = 20 // initialize virtual analog output 1 to 20
AVO1 + SRC4 Ig RMS = AVO3
The automation editing operators are shown in the following table.
Figure 344: Math example
// add an offset of 20 to the Ig RMS
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 8: AUTOMATION
38 38
to 3.402823 × 10 .
Eq. 42