Schweitzer Engineering Laboratories SEL-351 - Section 5: Trip and Target Logic; Trip Logic

Date Code 20001006 Trip and Target Logic 5-1
SEL-351 Instruction Manual
SECTION 5: TRIP AND TARGET LOGIC
TRIP LOGIC
The trip logic in Figure 5.1 provides flexible tripping with SELOGIC
®
Control Equation settings:
TRCOMM Communications-Assisted Trip Conditions.
Setting TRCOMM is supervised by communications-assisted trip logic.
See Communications-Assisted Trip Logic – General Overview later in
this section for more information on communications-assisted tripping.
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 separate
from setting TR for target LED purposes. (COMM target LED on the
front panel illuminates when DTT asserts to logical 1; see COMM target
LED discussion in the Front-Panel Target LEDs subsection at the end of
this section).
A typical setting for DTT is:
DTT = IN6
where input IN6 is connected to the output of direct transfer trip
communications equipment.
Setting DTT is also used for Direct Underreaching Transfer Trip (DUTT)
schemes.
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 5-7 for more
information on switch-onto-fault logic.
TR Other Trip Conditions.
Setting TR is the SELOGIC Control Equation trip setting most often used if
tripping does not involve communications-assisted (settings TRCOMM and
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. This is rising edge initiated timer. The settable range for
this timer is 4 - 16,000 cycles. See Figure 5.2.
Courtesy of NationalSwitchgear.com