Schweitzer Engineering SEL-2032, Instruction Manual

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4.8
SEL-2032 Communications Processor Instruction Manual Date Code 20120126
SEL
OGIC
Control Equations
Outputs
The following SEL
OGIC
control equation adds !D2 to the previous equation:
Equation 4.4
Now, as shown by Figure 4.7 , the trigger condition is only true momentarily;
then it retriggers upon completion of the message processing.
Figure 4.7 Forcing Retriggering Avoids Trigger Lock-Out
Processing
Sequence
You may need to consider the order in which SEL
OGIC
control equations are
processed to fully understand their operation and thereby ensure the desired
result. When a SEL
OGIC
control equation contains, as one of its terms, the
result of another SEL
OGIC
control equation, the order in which the equations
are processed may affect the result. For example, consider three SEL
OGIC
control equations, A, B, and C, that are processed in alphabetic order. It takes
1

s to process each equation, and the group is processed every 31 ms in the
SEL-2032. If SEL
OGIC
control equation B contains the results of equation A,
the results of B will be current (within 1

s) because A was processed as part
of the current process cycle. However, if equation B contains the results of
equation C, the results of B will not be current because the results of C are
from the previous process cycle, which is now one processing interval old.
The SEL-2032 processes SEL
OGIC
control equations in the order and
frequency shown in Table 4.2 . Figure 4.8 illustrates this processing sequence.
ISSUE2 1:UMB*!D2+2:UMB*!D2 =
Auto-Message
Operation
Completes, Causing
D2 to Retrigger
Completion of
\DAC2/ Processing
Clears 2:UMB
Completion of
\DAC1/ Processing
Clears 1:UMB
Auto-Message
Is Triggered
1:UMB Set
by New
Unsolicited
Messages
1:UMB
2:UMB
ISSUE2
D2
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