Thytronic NA11 User Manual

71
NA11 - Manual - 02 - 2009
FUNCTION CHARACTERISTICS
4.5 CONTROL AND MONITORING
Automatic reclosure (79)
Preface
The automatic reclosure function is well-used on overhead lines (when faults are self-extinguish
after tripping of protection relays).
Operation and settings
The following sequences may be selected:
Rapid reclosure,
Rapid reclosure followed by one slow reclosure,
Rapid reclosure followed by one slow reclosure and one or more delayed reclosures (1...5).
Starting of the automatic reclosing function can be raised by internal protective elements or exter-
nally by means binary input signals (eg: external protection device contacts or operating switches).
The following logics may be set (binary inputs allocation):
52a - 52b (Circuit breaker state); the CB position is indispensable for the auto reclosure function.
Blocking; exclusion command (pulse),
Enabling; activation command (pulse).
The following output functions may be coupled to the output relays:
CB reclosing command; it is indispensable for the auto reclosure function.
Reclosure fail.
Cycle in progress.
The following timers are provided:
t
rdt
Rapid reclosure dead time
t
sdt
Slow reclosure dead time
t
r
Reclaim time
t
d
Manual close fault discrimination time
t
d1
Slow reclosure fault discrimination time
t
d2
Delayed reclosure fault discrimination time.
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 extinction
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 mechanical
characteristics of the circuit breaker and the residual arc extinction.
Slow reclosure dead time (t
sdt
)
[1]
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 set-
ting mode.
Slow reclosure fault discrimination time (t
d1
) and Delayed reclosure fault discrimination time (t
d2
)
If any trip arises within the time interval t
d1
or t
d2
(slow or delayed reclosure), the cycle goes off and
the failed reclosure is issued.
Manual close fault discrimination time (t
d
)
If any trip arises within the time interval following the intentional close CB command , the cycle goes
off and the failed reclosure is issued; if no trip are detected the reclosing sequence goes on with the
programmed delayed reclosures.
Note 1 The reclosing waiting time is calculated from the fi rst event that is detected between the reset of the trip element and the open state acquisition
of the circuit breaker
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Thytronic NA11 Specifications

General

Brand	Thytronic
Model	NA11
Category	Relays
Language	English