5-4 Trip and Target Logic Date Code 20001006
SEL-351 Instruction Manual
The OPEN command is no longer directly embedded in the trip logic. This change was
made so that users can supervise the OPEN command if desired via setting TR.
The OPEN command is now included in the trip logic in the factory settings:
TR = … + OC
Relay Word bit OC asserts for execution of the OPEN Command. See OPE Command
(Open Breaker) in Section 10: Serial Port Communications and Commands for more
information on the OPEN Command. More discussion follows later on the factory settings
for setting TR.
If previous firmware versions of the SEL-351 Relay with the OPEN command imbedded
in the trip logic also have setting TR set as:
TR = … + OC
this would appear as a redundancy in inputting the OPEN command into the trip logic.
But, this is not a problem - just a redundancy in logic. Thus, SEL-351 Relays with
various firmware versions can be set the same with respect to setting TR = … + OC.
If a user wants to supervise the OPEN command with optoisolated input IN5, the
following setting is made:
TR = … + OC*IN5
With this setting, the OPEN command can provide a trip only if optoisolated input IN5 is
asserted. This is just one OPEN command supervision example - many variations are
possible.
To prevent the execution of the OPEN command from initiating reclosing, Relay Word bit
OC is entered in the SELOGIC Control Equation setting 79DTL (Drive-to-Lockout) in the
factory settings. See the Note in the Lockout State discussion, following Table 6.1.
A COMM target LED option for the OPEN command is discussed in the Front-Panel
Target LEDs subsection at the end of this section.
Unlatch Trip
Once Relay Word bit TRIP is asserted to logical 1, it remains asserted at logical 1 until all the
following conditions come true:
• Minimum Trip Duration Timer stops timing (logic output of the TDURD timer goes to
logical 0)
• Output of OR-1 gate deasserts to logical 0
• One of the following occurs:
− SELOGIC Control Equation setting ULTR asserts to logical 1,
− The front-panel TARGET RESET button is pressed,
− Or the TAR R (Target Reset) command is executed via the serial port.
Courtesy of NationalSwitchgear.com
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