Date Code 20020215
Setting SEL
OGIC
®
Control Equations
G-3
SEL-351R Instruction Manual
Other Relay Word Bits
The preceding example was for a phase time-overcurrent element, demonstrating Relay Word bit
operation for pickup, time-out, and reset conditions. Other Relay Word bits (e.g., those for
definite-time overcurrent elements, voltage elements, frequency elements) behave similarly in
their assertion or deassertion to logical 1 or logical 0, respectively. The time-overcurrent
elements (like the preceding phase time-overcurrent element example) are rather unique because
they have a Relay Word bit (e.g., 51P1R) 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: Overcurrent, Voltage, Synchronism Check, and Frequency Elements
through
Section 8: Breaker/Recloser Monitor, Battery System Monitor, Metering, and Load Profile
Functions
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 reclosers
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: 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.
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