10946
171
CIN9
2
Close
10947
171
CIN9
3
Bad
11008
172
CIN10
0
Intermediate
11009
172
CIN10
1
Open
11010
172
CIN10
2
Close
11011
172
CIN10
3
Bad
5.5.4. Auto-reclosing 0
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Autoreclosing (AR) means coordinated de-energization and energization of transmission or distribution
overhead-line with purpose to clear permanent or semi-permanent cause of fault from the line to
restore supply automatically to the line.
Autoreclosing can be used in overhead-line networks for clearing transient and semi-permanent faults
which present approximately 80-95% of all of the faults found in transmission and distribution networks.
Majority of this type of faults can be cleared with high speed autoreclosing and the rest of the faults
can be cleared with delayed autoreclosing by de-energizing the faulty line for a longer period of time.
Only minority of the overhead line faults are permanent type which require maintenance or repair in the
actual fault location. Faults like lightning in the line, tree branch touching to the overhead line, arc
caused by animals or short circuits caused by objects touching to the overhead lines are this type of
transient and semi-permanent faults. If the fault is permanent for example tree fall and leaning into the
overhead line or broken insulator, autoreclosing will not clear the fault and the faulty feeder shall be
locked from closing until the cause of the fault is repaired in the actual fault location. Also close short
circuit faults should avoid the autoreclosing to be even initiated in order to avoid unnecessary stress for
the lines and circuit breaker in cases when the fault cannot be cleared by autoreclosing the line. Similar
situations arise also in the mixed cable and overhead line networks since cable network faults cannot
be cleared by autoreclosing. In this category faults the autorecloser should be aware of fault location
before autoreclosing is applied to the faulty line.
Auto-reclosing as application
The main principle of autoreclosing is to de-energize the faulty line and fault location so that the cause
of the fault can drop out from the line. When the line is energized and object either touches or drops
into the line, current will start to flow through the object either to the ground or in between of the
phases causing the surrounding air to heat and ionize and start to operate as conductor in between of
the energized phase(s) and (or) ground causing arc to ignite.
When the breaker is opened either by command of autorecloser or protection function, voltage in the
line will be zero thus extinguishing the arc and letting the object which caused the fault to drop from the
line and by this way clearing the cause of the fault. Autorecloser closes the breaker after set time
(called Dead Time meaning the time which the line is not-energized) and the supply is restored to the
line. If the fault is not cleared by this rst autoreclosing cycle (called Shot) then more shots can be
applied to the line.
If the fault was not cleared by the time autorecloser closes the breaker and second shot is applied into
the line there can be set either time delay (called Arcing time) in order to burn the fault causing object
from the line or normal protection operating times can be applied. In autorecloser is selection also if the
fault is not present when closing the breaker but reappears soon after closing the breaker (called
Discrimination time, Reclaim time), Autorecloser either arms another shot or gives nal trip command
and locks-out. In case one shot is applied to the line and if it is not successfully clearing the fault
autorecloser will init nal trip and will lock out the feeder closing also.
Whether single or multi-shot autoreclosing should be used is matter of the type of protection,
switchgear, circuit breaker, stability requirements, network type, consumer loads and also local utility
knowledge and practices of the network.
AQ-F255
Instruction manual
Version: 2.00
© Arcteq Relays Ltd
218
