4.16
SEL-587Z Instruction Manual Date Code 20020903
Control Logic
Trip Logic (TRn, ULTRn, TDURD)
Trip Logic (TRn, ULTRn, TDURD)
The trip logic in Figure 4.7 provides flexible tripping with the following three
SEL
OGIC control equation settings:
TRn–Trip Conditions
ULTRn–Unlatch Trip Conditions
TDURD–Minimum Trip Duration Time
Figure 4.7 Trip Logic.
Set Trip
Any time setting TRn = logical 1, Relay Word bit TRIPn asserts to logical 1,
regardless of other trip logic conditions.
As shown in the time line example in Figure 4.7, 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 TRn = logical 1 beyond the
TDURD time, Relay Word bit TRIPn remains asserted at logical 1 for as long
as TRn = logical 1. In this case, when TRn finally deasserts (TRn = logical 0),
the TRIPn Relay Word bit deasserts immediately, i.e., the TDURD time is not
considered again.
Unlatch Trip
Once Relay Word bit TRIPn is asserted to logical 1, it remains asserted at
logical 1 until both of these conditions are true:
Trip Duration Timer stops timing (output of the TDURD timer
goes to logical 0).
SELOGIC control equation setting TRn deasserts to logical 0.
Example operation
of SEL
OGIC control
equation setting TRn
(input into Minimum Trip
Duration Timer and OR–1)
Resultant logic
output of Minimum Trip
Duration Timer (input into OR–1)
Rising-edge
input occurring
when the Minimum
Trip Duration Timer is reset
OR–combination of above
two logic traces (inputs into
OR–1 to drive Relay Word bit TRIPn)
0
TDURD
Minimum Trip
Duration Timer
rising-edge detect
TRIPn
Relay
Word
Bit
OR
1
(out)
(in)
ULTRn
TDURD TDURD TDURD
TARGET RESET
Pushbutton
TAR R
Serial Port Command
TRn
Setting
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