5.3
Date Code 20060320 Instruction Manual SEL-311C Relay
Trip and Target Logic
Trip Logic
Set Trip
Refer to Figure 5.1. All trip conditions:
➤ Communications-Assisted Trip, including Direct Transfer Trip
➤ Switch-Onto-Fault Trip
➤ Other Trips
are combined into OR-1 gate. The output of OR-1 gate asserts Relay Word bit
TRIP to logical 1, regardless of other trip logic conditions. It also is routed
into the Minimum Trip Duration Timer (setting TDURD).
As shown in the time line example in Figure 5.2, the Minimum Trip Duration
Timer (with setting TDURD) outputs a logical 1 for a time duration of
“TDURD” cycles any time it sees a rising edge on its input (logical 0 to
logical 1 transition), if it is not already timing (timer is reset). The TDURD
timer ensures that the TRIP Relay Word bit remains asserted at logical 1 for a
minimum of “TDURD” cycles. If the output of OR-1 gate is logical 1 beyond
the TDURD time, Relay Word bit TRIP remains asserted at logical 1 for as
long as the output of OR-1 gate remains at logical 1, regardless of other trip
logic conditions.
The Minimum Trip Duration Timer can be set no less than four cycles.
Figure 5.2 Minimum Trip Duration Timer Operation
(See Bottom of Figure 5.1)
The OPEN command is included in the trip logic in the factory settings:
TR = … + OC
Relay Word bit OC asserts for execution of the OPEN Command. See OPE
Command (Open Breaker) on page 10.36 for more information on the OPEN
Command. More discussion follows later on the factory settings for setting
TR.
If a user wants to supervise the OPEN command with optoisolated input
IN105, the following setting is made:
TR = … + OC * IN105
Example output of
OR-1 (input into
Minimum Trip
Duration Timer and
OR-2)
Resultant logic
output of Minimum
Trip Duration Timer
(input into OR-2)
OR-combination of
above two logic
traces (inputs into
OR-2 to drive Relay
Word bit TRIP)
Rising edge
input occurring
when the
Minimum
Trip Duration
Timer is reset
TDURD
TDURD
TDURD
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