Date Code 20011205
Trip and Target Logic
5-1
SEL-311B Instruction Manual
SECTION 5: TRIP AND TARGET LOGIC
T
RIP
L
OGIC
The trip logic in Figure 5.1 provides flexible tripping with SEL
OGIC
®
control equation settings:
DTT
Direct Transfer Trip Conditions.
Note in Figure 5.1 that setting DTT is unsupervised. Any element that
asserts in setting DTT will cause Relay Word bit TRIP to assert to
logical 1.
Although setting TR is also unsupervised, setting DTT is provided
separately from setting TR for target LED purposes. (DT target LED on
the front panel illuminates when DTT asserts to logical 1; see DT target
LED discussion in the
Front-Panel Target LEDs
subsection at the end of
this section).
Typical settings for DTT are:
DTT = IN106 or DTT = RMB1A
where input IN106 is connected to the output of direct transfer trip
communications equipment or receive M
IRRORED
B
IT
RMB1A is asserted
by the transfer trip condition in a remote SEL relay.
TRSOTF
Switch-Onto-Fault Trip Conditions.
Setting TRSOTF is supervised by the switch-onto-fault condition SOTFE.
See
Switch-Onto-Fault (SOTF) Trip Logic
on page 5-6 for more
information on switch-onto-fault logic.
TR
Other Trip Conditions.
Setting TR is the SEL
OGIC
control equation trip setting
most often used
if
tripping does not involve DTT or switch-onto-fault (setting TRSOTF) trip
logic.
Note in Figure 5.1 that setting TR is unsupervised. Any element that
asserts in setting TR will cause Relay Word bit TRIP to assert to logical 1.
ULTR
Unlatch Trip Conditions.
TDURD
Minimum Trip Duration Time.
This timer establishes the minimum time duration for which the TRIP
Relay Word bit asserts. The settable range for this timer is 4–16,000
cycles. See Figure 5.2.
More than one trip setting (or all three trip settings DTT, TRSOTF, and TR) can be set. For
example, in a direct trip scheme, DTT is set with a direct trip contact input, TR is set with
direction forward underreaching Zone 1 distance elements and other time delayed elements (e.g.,
Zone 2 definite-time distance elements), and TRSOTF is set with instantaneous directional and
non-directional elements.
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