Schweitzer Engineering Laboratories SEL-787, Instruction Manual, Page: 154 / 564

4.76
SEL-787 Relay Instruction Manual Date Code 20081022
Protection and Logic Functions
Logic Settings (SET L Command)
Math Negation Operator (–)
The negation operator – changes the sign of a numerical value. For example:
MV01 := RB01
When Remote bit RB01 asserts, Math variable MV01 has a value of 1, i.e.,
MV01 = 1. We can change the sign on MV01 with the following expression:
MV01 := – 1 * RB01
Now, when Remote bit RB01 asserts, Math variable MV01 has a value of –1,
i.e., MV01 = –1.
Boolean NOT Operator (NOT)
Apply the NOT operator to a single Relay Word bit and to multiple elements
(within parentheses).
An example of a single Relay Word bit is as follows:
SV01 := NOT RB01
When Remote bit RB01 asserts from logical 0 to logical 1, the Boolean NOT
operator, in turn, changes the logical 1 to a logical 0. In this example, SV01
deasserts when RB01 asserts.
Following is an example of the NOT operator applied to multiple elements
within parentheses.
The Boolean SEL
OGIC
control equation OUT101 setting could be set as
follows:
OUT101 := NOT(RB01 OR SV02)
If both RB01 and SV02 are deasserted (= logical 0), output contact OUT101
asserts, i.e., OUT101 := NOT (logical 0 OR logical 0) = NOT
(logical 0) = logical 1.
In a Math SEL
OGIC
control equation, use the NOT operator with any Relay
Word bits. This allows a simple if/else type equation, as shown in the example
below.
MV01 := 12 * IN101 + (MV01 + 1) * NOT IN101
The equation above sets MV01 to 12 whenever IN101 asserts, otherwise it
increments MV01 by 1 each time the equation is executed.
Boolean Rising-Edge Operator (R_TRIG)
Apply the rising-edge operator, R_TRIG, to individual Relay Word bits only;
you cannot apply R_TRIG to groups of elements within parentheses. When
any Relay Word bit asserts (going from logical 0 to logical 1), R_TRIG
interprets this logical 0 to logical 1 transition as a “rising edge” and asserts to
logical 1 for one processing interval.
For example, the Boolean SEL
OGIC
control equation event report generation
setting uses rising-edge operators:
ER := R_TRIG IN101 OR R_TRIG IN102
The rising-edge operators detect a logical 0 to logical 1 transition each time
one of IN101 or IN102 asserts. Using these settings, the device triggers a new
event report each time IN101 or IN102 asserts anew, if the device is not
already recording an event report. You can use the rising-edge operator with