Schweitzer Engineering Laboratories SEL-421-4, Instruction Manual

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13.28
SEL-400 Series Relays Instruction Manual Date Code 20171006
SEL
OGIC
Control Equation Programming
SEL
OGIC
Control Equation Operators
The argument of an F_TRIG statement must be a single bit within the relay. An
example of the relay detecting a falling edge of a calculated quantity is shown in
Example 13.11 .
Comparison
Comparison is a mathematical operation that compares two numerical values
with a result of logical 0 or logical 1. AND and OR operators compare Boolean
values; comparison functions compare floating-point values such as currents and
other quantities. Comparisons and truth tables for operation of comparison func-
tions are shown in
Table 13.21 .
NOTE:
Be careful how you use the
equal (=) and the inequality (<>)
operators. Because the relay uses a
floating-point format to calculate
analog values, only integer numbers
will match exactly. Allow a small
hysteresis of the following form:
PSV01 := I01FM < 10.002 AND
I01FM > 9.988.
Figure 13.10 F_TRIG Timing Diagram
Example 13.11 F_TRIG Operation
The SEL
OGIC
control equation below shows an invalid use of the F_TRIG
operation.
ASV015 := F_TRIG (ASV001 AND ALT11) # Invalid statement, do
not use
Use a SEL
OGIC
control equation variable to calculate the quantity and then
use the F_TRIG operation on the result, as shown below.
ASV014 := ASV001 AND ALT11 # Calculate quantity in an intermedi-
ate result variable
ASV015 := F_TRIG ASV14 # Perform an F_TRIG on the quantity
Relay Word bit A
F_TRIG A
F_TRIG A
Deasserts
F_TRIG A
Asserts
Relay Word bit A Changes
from 1 to 0
1
Processing
Interval
1
Processing
Interval
Table 13.21 Comparison Operations
A B A > B A

B A = B A <> B A

B A < B
6.35 7.00 0 0 0 1 1 1
5.10 5.10 0 1 1 0 1 0
4.25 4.00 1 1 0 1 0 0