4.60
SEL-751A Relay
Instruction Manual
Date Code 20100129
Protection and Logic Functions
Reclose Logic
Reclosing Relay
States and General
Operation
explains in general the different states of the reclosing relay and
its operation.
Figure 4.34
Reclosing Relay States and General Operation
The reclosing relay is in one (and only one) of these states (listed in
) at any time. When in a given state, the corresponding Relay Word
bit asserts to logical 1, and the LED illuminates. Automatic reclosing only
takes place when the relay is in the Reclose Cycle State.
Lockout State
All Automatic
Reclosing Attempts
Unsuccessful
Unsuccessful
Reclose Initiation
Other Lockout Conditions
Power Up
Reset
Timer
Times
Out
Reset
Timer
Times
Out
Other
Lockout
Conditions
Unsuccessful
Reclose
Initiation
Successful
Reclose
Initiation
Successful
Reclose
Initiation
Maintained
Lockout
Condition
Reset State
The circuit breaker has been closed
for a qualifying reset time. The SEL-751A
is ready to go through an automatic
reclosing sequence in the reclose cycle
state if the circuit breaker trips open
and reclose initiation is successful.
Relay Word bit 79RS = logical 1
Front-panel
RS
LED illuminated
Reclose Cycle State
The SEL-751A automatically recloses the
circuit breaker after each successful
reclose initiation and corresponding set
open interval time.
Relay Word bit 79CY = logical 1
Front-panel
CY
LED illuminated
All automatic reclosing attempts are
unsuccessful, reclose initiation is unsuccessful,
other lockout conditions occur, or the SEL-751A
powers up. The relay returns to the reset state
after the circuit breaker is closed, the reset
timer times out, and there are no maintained
lockout conditions.
Relay Word bit 79LO = logical 1
Front-panel
LO
LED illuminated
Table 4.26
Relay Word Bit and Front-Panel Correspondence to Reclosing
Relay States
Reclosing Relay State
Corresponding Relay
Word Bit
Corresponding
Front-Panel LED
Reset
79RS
RS
Reclose Cycle
79CY
CY
Lockout
79LO
LO
Summary of Contents for 751A
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