G.5
Date Code 20080213
Instruction Manual
SEL-351A Relay
Setting SEL
OGIC
Control Equations
SEL
OGIC
Control Equations
Example of NOT Operator ! Applied to Single Element
The internal circuit breaker status logic in the SEL-351A operates on 52a
circuit breaker auxiliary contact logic. The SEL
OGIC
control equation circuit
breaker status setting is labeled 52A. See
Optoisolated Inputs on page 7.2
and
for more information on SEL
OGIC
control equation
circuit breaker status setting 52A.
When a circuit breaker is closed, the 52a circuit breaker auxiliary contact is
closed. When a circuit breaker is open, the 52a contact is open.
The opposite is true for a 52b circuit breaker auxiliary contact. When a circuit
breaker is closed, the 52b circuit breaker auxiliary contact is open. When the
circuit breaker is open, the 52b contact is closed.
If a 52a contact is connected to optoisolated input
IN101
, the SEL
OGIC
control
equation circuit breaker status setting 52A is set:
52A =
IN101
Conversely, if a 52b contact is connected to optoisolated input
IN101
, the
SEL
OGIC
control equation circuit breaker status setting 52A is set:
52A =
!IN101
[=NOT(IN101)]
With a 52b contact connected, if the circuit breaker is closed, the 52b contact
is open and input
IN101
is de-energized [IN101 = 0 (logical 0)]:
52A =
!IN101
= NOT(IN101) = NOT(0) = 1
Thus, the SEL
OGIC
control equation circuit breaker status setting 52A sees a
closed circuit breaker.
With a 52b contact connected, if the circuit breaker is open, the 52b contact is
closed and input
IN101
is energized [IN101 = 1 (logical 1)]:
52A =
!IN101
= NOT(IN101) = NOT(1) = 0
Thus, the SEL
OGIC
control equation circuit breaker status setting 52A sees an
open circuit breaker.
Example of NOT Operator ! Applied to Multiple Elements (Within
Parentheses)
The SEL
OGIC
control equation trip unlatch setting is set as follows:
ULTR =
!(51P + 51G)
In this factory setting example, the unlatch condition comes true only when
both the 51P (phase time-overcurrent element pickup indication) and 51G
(residual-ground time-overcurrent element pickup indication) Relay Word bits
deassert:
ULTR =
!(51P + 51G)
= NOT(51P + 51G)
As stated previously, the logic within the parentheses is performed first. In this
example, the states of Relay Word bits 51P and 51G are ORed together. Then
the NOT operator is applied to the logic resultant from the parentheses.
If either one of 51P or 51G is still asserted [e.g., 51G = 1 (logical 1)], the
unlatch condition is not true:
ULTR =
NOT(51P + 51G)
= NOT(0 + 1) = NOT(1) = 0
Содержание SEL-351A
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