5-16 Trip and Target Logic Date Code 20001006
SEL-351 Instruction Manual
EBLKD – Echo Block Delay
Prevents echoing of received PT for settable delay after dropout of local permissive elements in trip
setting TRCOMM – typically set at 10 cycles. Set to OFF to defeat EBLKD.
ETDPU – Echo Time Delay Pickup
Sets minimum time requirement for received PT, before echo begins – typically set at 2 cycles. Set
to OFF for no echo.
EDURD – Echo Duration
Limits echo duration, to prevent channel lockup – typically set at 3.5 cycles.
Logic Outputs
The following logic outputs can be tested by assigning them to output contacts. See Output
Contacts in Section 7: Inputs, Outputs, Timers, and Other Control Logic for more information
on output contacts.
Z3RB – Zone (Level) 3 Reverse Block
Current-reversal guard asserted (operates as an input into the trip logic in Figure 5.1 and the
DCUB logic in Figure 5.10).
ECTT – Echo Conversion to Trip
PT received, converted to a trip condition for a Weak-Infeed Condition (operates as an input into
the trip logic in Figure 5.1).
KEY – Key Permissive Trip
Signals communications equipment to transmit permissive trip. For example, SELOGIC Control
Equation setting OUT5 is set:
OUT5 = KEY
Output contact OUT5 drives a communications equipment transmitter input in a two-terminal line
application (see Figure 5.8).
In a three-terminal line scheme, output contact OUT7 is set the same as OUT5 (see Figure 5.9):
OUT7 = KEY
EKEY – Echo Key Permissive Trip
Permissive trip signal keyed by Echo logic (used in testing).
Courtesy of NationalSwitchgear.com
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