Date Code 20001006
Setting SEL
OGIC
®
Control Equations
G-3
SEL-351 Instruction Manual
the preceding phase time-overcurrent element example) are rather unique because they have a
Relay Word bit (e.g., 51PR) that asserts for the reset state of the element.
Relay Word bits are used in SEL
OGIC
Control Equations, which are explained in the following
subsection.
SEL
OGIC
C
ONTROL
E
QUATIONS
Many of the protection and control element logic inputs shown in the various figures in
Section 3
through
Section 8
are SEL
OGIC
Control Equations (labeled “SEL
OGIC
Settings” in most of the
Figures). SEL
OGIC
Control Equations are set with combinations of Relay Word bits to accomplish
such functions as:
•
tripping circuit breakers
•
assigning functions to optoisolated inputs
•
operating output contacts
•
torque-controlling overcurrent elements
•
switching active setting groups
•
enabling/disabling reclosing
Traditional or advanced custom schemes can be created with SEL
OGIC
Control Equations.
SEL
OGIC
Control Equation Operators
SEL
OGIC
Control Equation settings use logic similar to Boolean algebra logic, combining Relay
Word bits together using one or more of the six SEL
OGIC
Control Equation operators listed in
Table G.1.
Table G.1: SEL
OGIC
Control Equation Operators (Listed in Processing Order)
Operator
Logic Function
/
rising edge detect
\
falling edge detect
()
parentheses
!
NOT
*
AND
+
OR
Operators in a SEL
OGIC
Control Equation setting are processed in the order shown in Table G.1.
Summary of Contents for SEL-351
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