Schweitzer Engineering SEL-351P - Program an Output for Tripping; Switch-Onto-Fault (SOTF) Trip Logic

Date Code 990215 Trip and Target Logic 5-5
SEL-351P Manual Técnico
See Figure 1.19 in Section 1: Factory-Set Logic for more information on factory-set SEL OGIC
Control Equation setting TR.
Program an Output for Tripping
The final trip/close logic in Figure 7.29 (that has input from
Figure SECTION 5: .1) controls
dedicated trip and close output contacts.
If additional trip output contacts are needed, program the extra output contacts with the TRIP
(
Figure SECTION 5: .1) or WBTR (Figure 7.29) Relay Word bits, depending on the application
(e.g., OUT101 = TRIP; OUT102 = WBTR). Examples of uses for additional trip output
contacts:
• Tripping more than one breaker
• Keying an external breaker failure relay
• Keying communication equipment in a Direct Transfer Trip scheme
See Output Contacts in Section 7: Inputs, Outputs, Timers, and Other Control Logic for more
information on programming output contacts.
S WITCH -O NTO -F AULT (SOTF) T RIP L OGIC
Switch-Onto-Fault (SOTF) trip logic provides a programmable time window for selected
elements to trip right after the circuit breaker closes. “Switch-onto-fault” implies that a circuit
breaker is closed into an existing fault condition. For example, suppose safety grounds are
accidentally left attached to a line after a clearance. If the circuit breaker is closed into such a
condition, the resulting fault needs to be cleared right away and reclosing blocked. An
instantaneous overcurrent element is usually set to trip in the three-pole open (3PO) logic and the
SOTF trip logic.
Refer to the SOTF trip logic in
Figure SECTION 5: .1 (middle of figure). The SOTF trip logic
permits tripping if both
the following occur:
• An element asserts in SEL
OGIC Control Equation trip setting TRSOTF
• Relay Word bit SOTFE is asserted to logical 1
Relay Word bit SOTFE (the output of the SOTF logic) provides the effective time window for an
element in trip setting TRSOTF (e.g., TRSOTF = 50P2) to trip after the circuit breaker closes.
Figure SECTION 5: .3 and the following discussion describe the three-pole open (3PO) logic
and the SOTF logic.