6.22
SEL-351A Relay Instruction Manual Date Code 20080213
Close and Reclose Logic
Reclosing Relay
Relay Word bit OC asserts for execution of the OPEN command. See the
Note in the Lockout State on page 6.13.
The drive-to-last shot factory setting is:
79DLS = 79LO
One open interval is also set in the factory settings, resulting in last shot = 1.
Any time the relay is in the lockout state (Relay Word bit 79LO = logical 1),
the relay is driven to last shot (if the shot counter is not already at a shot value
greater than or equal to shot = 1):
79DLS = 79LO = logical 1
Thus, if optoisolated input IN102 (reclose enable switch) is in the “disable
reclosing” position (Relay Word bit IN102 = logical 0) or local bit LB3
(manual trip switch) is operated, then the relay is driven to the Lockout State
(by setting 79DTL) and, subsequently, last shot (by setting 79DLS).
Additional Settings Example 1
The preceding drive-to-lockout factory settings example drives the relay to the
Lockout State immediately when the reclose enable switch (optoisolated input
IN102) is put in the “reclosing disabled” position (Relay Word bit IN102 =
logical 0):
79DTL = !IN102 + ... = NOT(IN102) + ... = NOT(logical 0) + ... = logical 1
To disable reclosing, but not drive the relay to the Lockout State until the relay
trips, make settings similar to the following:
79DTL = !IN102 * TRIP + ...
Additional Settings Example 2
To drive the relay to the Lockout State for fault current above a certain level
when tripping (e.g., level of phase instantaneous overcurrent element 50P3),
make settings similar to the following:
79DTL = TRIP * 50P3 + ...
Additionally, if the reclosing relay should go to the Lockout State for an
underfrequency trip, make settings similar to the following:
79DTL = TRIP * 81D1T + ...
Other Settings Considerations
If no special drive-to-lockout or drive-to-last shot conditions are desired, make
the following settings:
79DTL = 0 (numeral 0)
79DLS = 0 (numeral 0)
With settings 79DTL and 79DLS inoperative, the relay still goes to the
Lockout State (and to last shot) if an entire automatic reclose sequence is
unsuccessful.
Overall, settings 79DTL or 79DLS are needed to take the relay to the Lockout
State (or to last shot) for immediate circumstances.
Courtesy of NationalSwitchgear.com
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