G.4
SEL-351A Relay Instruction Manual Date Code 20080213
Setting SELOGIC Control Equations
SEL
OGIC Control Equations
SELOGIC Control Equations
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 Monitor and Metering are
SEL
OGIC control equations (labeled “SELOGIC 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.
SELOGIC Control
Equation Operators
SELOGIC 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.
Operators in a SEL
OGIC control equation setting are processed in the order
shown in Table G.1.
SELOGIC Control Equation Parentheses Operator ( )
More than one set of parentheses ( ) can be used in a SELOGIC control
equation setting. For example, the following SEL
OGIC control equation setting
has two sets of parentheses:
SV7 = (SV7 + IN101) * (50P1 + 50N1)
In the above example, the logic within the parentheses is processed first and
then the two parentheses resultants are ANDed together. The above example is
from Figure 7.25. Parentheses cannot be “nested” (parentheses within
parentheses) in a SEL
OGIC control equation setting.
SELOGIC Control Equation NOT Operator !
The NOT operator ! is applied to a single Relay Word bit and also to multiple
elements (within parentheses). Following are examples of both.
Ta b le G . 1 S EL OGIC Control Equation Operators (Listed in Processing Order)
Operator Logic Function
/ rising-edge detect
\ falling-edge detect
() parentheses
!NOT
* AND
+OR
Courtesy of NationalSwitchgear.com
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