Schweitzer Engineering Laboratories SEL-2020 - SECTION 7: SELOGIC CONTROL EQUATIONS

Date Code 20010518 SELOGIC Control Equations i
SEL-2020 Instruction Manual
TABLE OF CONTENTS
SECTION 7: SELOGIC
®
CONTROL EQUATIONS 7-1
Introduction...................................................................................................................................7-1
Operation.......................................................................................................................................7-1
Inputs.............................................................................................................................................7-2
Global Elements ....................................................................................................................7-2
Local Elements......................................................................................................................7-2
Relay Elements......................................................................................................................7-2
Status Information .................................................................................................................7-3
Database Bits as Elements.....................................................................................................7-3
Timed Conditions..................................................................................................................7-3
Equation Syntax ............................................................................................................................7-4
Operators ...............................................................................................................................7-4
Operator Precedence .............................................................................................................7-4
Limitations ............................................................................................................................7-5
Equation Disabling................................................................................................................7-5
Outputs ..........................................................................................................................................7-5
Contact Outputs.....................................................................................................................7-5
Global Intermediate Logic.....................................................................................................7-5
Local Intermediate Logic ......................................................................................................7-5
Message Triggers ..................................................................................................................7-6
Processing Sequence .............................................................................................................7-9
TABLES
Table 7.1: Unacceptable SELOGIC Control Equation Operator Combinations ........................................7-5
FIGURES
Figure 7.1: SELOGIC Control Equations Inputs and Outputs ...................................................................7-1
Figure 7.2: Example of Latch Operation...................................................................................................7-6
Figure 7.3: Message Triggering Logic......................................................................................................7-6
Figure 7.4: Normal Auto-Message Trigger...............................................................................................7-7
Figure 7.5: Unsuccessful Auto-Message Trigger......................................................................................7-7
Figure 7.6: Trigger Lock-Out Problem .....................................................................................................7-8
Figure 7.7: Forcing Re-triggering Avoids Trigger Lock-Out ...................................................................7-8
Figure 7.8: Processing Sequence Illustration............................................................................................7-9