3.29
Date Code 20110408 Instruction Manual SEL-551 Relay
Relay Elements and Logic
Reclosing Relay
If no reclose initiate supervision is desired, make the following setting:
79RIS = 1 (numeral 1)
Setting 79RIS = logical 1 at all times. Any time a logical 0 to logical 1
transition is detected by setting 79RI, open interval timing will be initiated
(unless prevented by some other means).
As discussed previously, if any one of the following settings are made:
79RI = 0 (numeral 0)
79RIS = 0 (numeral 0)
the reclosing relay does not exist.
Drive-to-Lockout and
Drive-to-Last Shot
Settings (79DTL and
79DLS, Respectively)
When 79DTL = logical 1, the reclosing relay goes to the Lockout State (Relay
Word bit 79LO = logical 1) and the front-panel LO (Lockout) LED illuminates.
When 79DLS = logical 1, the reclosing relay goes to the last shot, if the shot
counter is not at a shot value greater than or equal to the calculated last shot
(see preceding discussions on last shot determination and the shot counter).
Factory Settings Example
The drive-to-lockout factory setting is:
79DTL = !LB1 + LB3
Local bit LB1 is set to operate as a reclose enable switch (see Local Control
Switches on page 3.5). When Relay Word bit LB1 = logical 1 (reclosing
enabled), the relay is not driven to the Lockout State (assuming local bit LB3
= logical 0, too):
!LB1 = !(logical 1) = NOT(logical 1) = logical 0
79DTL = !LB1 + LB3 = (logical 0) + LB3 = LB3
When Relay Word bit LB1 = logical 0 (reclosing disabled), the relay is driven
to the Lockout State:
!LB1 = !(logical 0) = NOT(logical 0) = logical 1
79DTL = !LB1 + LB3 = (logical 1) + LB3 = logical 1
Local bit LB3 is set to operate as a manual trip switch (see Local Control
Switches and Trip Logic on page 3.17). When Relay Word bit LB3 = logical 0
(no manual trip), the relay is not driven to the Lockout State (assuming local
bit LB1 = logical 1, too):
79DTL = !LB1 + LB3 = NOT(LB1) + (logical 0) = NOT(LB1)
When Relay Word bit LB3 = logical 1 (manual trip), the relay is driven to the
Lockout State:
79DTL = !LB1 + LB3 = NOT(LB1) + (logical 1) = logical 1
The drive-to-last shot factory setting is:
79DLS = 79LO
NOTE: See OPE Command (Open) for
a possible 79DTL setting for SEL-551
relays with early firmware versions.
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