5.5
Date Code 20080213 Instruction Manual SEL-351A Relay
Trip and Target Logic
Trip Logic
➤ Relay Word bit OC asserts for execution of the OPEN
command. See OPE Command (Open Breaker) on page 10.35
for more information on the OPEN command.
With setting TDURD = 9.00 cycles, once the TRIP Relay Word bit asserts via
SEL
OGIC control equation setting TR, it remains asserted at logical 1 for a
minimum of 9 cycles.
Unlatch Trip
In SELOGIC control equation setting
ULTR = !(51P + 51G)
Both time-overcurrent element pickups 51P and 51G must be deasserted
before the trip logic unlatches and the TRIP Relay Word bit deasserts to
logical 0.
ULTR = !(51P + 51G) = NOT(51P + 51G) = NOT(51P) * NOT(51G)
Additional Settings
Examples
The factory setting for SELOGIC control equation setting ULTR is a current-
based trip unlatch condition. A circuit breaker status unlatch trip condition can
be programmed as shown in the following examples.
Unlatch Trip With 52a Circuit Breaker Auxiliary Contact
A 52a circuit breaker auxiliary contact is wired to optoisolated input IN101.
52A = IN101 (SELOGIC control equation circuit breaker status setting—see
Optoisolated Inputs on page 7.2)
ULTR = !IN101
Input IN101 has to be de-energized (52a circuit breaker auxiliary contact has to
be open) before the trip logic unlatches and the TRIP Relay Word bit deasserts
to logical 0.
ULTR = !IN101 = NOT(IN101)
Unlatch Trip With 52b Circuit Breaker Auxiliary Contact
A 52b circuit breaker auxiliary contact is wired to optoisolated input IN101.
52A = !IN101 (SELOGIC control equation circuit breaker status setting—
see Optoisolated Inputs)
ULTR = IN101
Input IN101 must be energized (52b circuit breaker auxiliary contact has to be
closed) before the trip logic unlatches and the TRIP Relay Word bit deasserts
to logical 0.
Courtesy of NationalSwitchgear.com
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