Schweitzer Engineering Laboratories SEL-311L, Instruction Manual, Page: 693 / 734

Date Code 20010625 Setting SEL
OGIC
®
Control Equations G-3
SEL-311L 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 unusual 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.