Sel 551 - Trip Logic

3.17
Date Code 20110408 Instruction Manual SEL-551 Relay
Relay Elements and Logic
Trip Logic
Trip Logic
The trip logic in Figure 3.13 provides flexible tripping with SELOGIC control
equation settings:
TR . Trip Conditions
ULTR . Unlatch Trip Conditions
and setting:
TDURD Minimum Trip Duration Time
Figure 3.13 Trip Logic
Set Trip
Any time setting TR = logical 1, Relay Word bit TRIP asserts to logical 1,
regardless of other trip logic conditions.
As shown in the time line example in Figure 3.13, the Minimum Trip Duration
Timer (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. The TDURD timer assures that the TRIP
Relay Word bit remains asserted at logical 1 for a minimum of “TDURD”
cycles. If SEL
OGIC control equation setting TR = logical 1 beyond the
TDURD time, Relay Word bit TRIP remains asserted at logical 1 for as long
as TR = logical 1.
Execution of the serial communications port OPEN command causes the
TRIP Relay Word bit to assert to logical 1 if the TDURD timer is set greater
than zero (0) cycles.
TDURD
TDURD TDURD
Example operation
of SELOGIC setting TR
(input into Minimum
Trip Duration Timer
and OR-1)
Resultant logic
output of Minimum
Trip Duration Timer
(input into OR-1)
OR-combination of
above two logic
traces (input into
OR-1 to drive Relay
Word bit TRIP)
OPEN
Command
SEL
OGIC
Settings
TR
ULTR
TARGET
RESET
Pushbutton
TAR R
Serial Port
Command
OR
1
Minimum
Trip
Duration
Timer
(in)
(out)
rising edge
detect
Relay
Word
Bit
TRIP
TRGTR
Rising edge input
occuring when the
Minimum Trip Duration
Timer is reset
0
TDURD