FUNCTION CHARACTERISTICS
42
NA011 - Manual - 05 - 2022
• Rapid reclosure dead time (
t
rdt
)
[1]
It is the time interval from the CB opening command and the CB reclosing command.
The setting time for the rapid reclosure is a compromise from the time required for the arc extinc-
tion on the fault location and the max allowable out of service time of the line.
The parameter must be adjusted on the basis of the extension and grid voltage. The minimum value
should allow the arc deionization and the insulation restoring in order to comply with the mechani-
cal characteristics of the circuit breaker and the residual arc extinction.
• Slow reclosure dead time (
t
sdt
)
[2]
It is the time interval from the failed fast reclosure and the start of slow reclosure sequence.
The setting time for the waiting time is a function of the mechanical characteristics of the circuit
breaker (data must be supplied by manufacturer). For newest circuit breakers typical values are
60 s and 180 s for oldest circuit breakers.
• Reclaim time (
t
r
)
It is the time interval following the initiation of reclosure command.
If no trip operation arises within the reclaim time the reclosing operation is regarded as successful
and the device is ready for a new sequence.
If any trip arises within the reclaim time the cycle goes on with sequence depending from the
setting mode.
• Slow reclosure fault discrimination time (
t
d
).
If any trip arises within the time interval
t
d
, the cycle goes off and the failed reclosure is issued.
Rapid reclosing
With Rapid-reclose setting (79
Mode = Rapid
), if no faults (CB opening command) occurs within the
reclaim time (Successful rapid reclosure), after the reclaim time the system comes back to reset; a
new trip starts a rapid reclosing sequence again. Any trip within the
t
r
time interval causes a block-
ing of the sequence and a failed reclosure signal is issued (unsuccessful rapid reclosure);
Unsuccessful rapid reclosure; new fault (CB opening command) occurs within the reclaim time.
The automatic reclosing system is blocked and a failed reclosure command is issued.
After the reclaim time, following a closed CB condition without any faults, the system comes back
to reset.
Note 1 The reclosing waiting time is calculated from the first event that is detected between the reset of the trip element and the open state acquisition
of the circuit breaker
Note 2 The reclosing waiting time is calculated from the first event that is detected between the reset of the trip element and the open state acquisition
of the circuit breaker
CB CLOSED
CB OPEN
CB CLOSED
79-diafram.ai
t
rdt
CB State
t
t
r
Successfully rapid reclosure
Reclaim timer
CB CLOSED CB OPEN
CB OPEN
CB CLOSED
79RF-diafram.ai
t
rdt
CB State
t
Unsuccessful rapid reclosure
CB CLOSED
Reclaim timer
Failed reclosure
t
t
r
t
r