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Autoreclosure

Autoreclosures are circuit breakers that automatically close after opening due to temporary faults, improving service reliability by restoring supply without manual intervention. They are typically used in overhead distribution systems, where about 80% of faults are transient and self-clearing. These devices can be programmed for multiple trips and are designed to handle lower power levels in smaller network sections, minimizing the need for costly manual resets.

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Ankit Joshi
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53 views8 pages

Autoreclosure

Autoreclosures are circuit breakers that automatically close after opening due to temporary faults, improving service reliability by restoring supply without manual intervention. They are typically used in overhead distribution systems, where about 80% of faults are transient and self-clearing. These devices can be programmed for multiple trips and are designed to handle lower power levels in smaller network sections, minimizing the need for costly manual resets.

Uploaded by

Ankit Joshi
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Autoreclosure

Autoreclosure

• An autoreclosure is a circuit breaker equipped with a


mechanism that can automatically close the breaker
after it has been opened due to a fault.
• These are used on overhead distribution systems to
interrupt temporary faults.
• It has been found that about 80% of the faults are
transient faults which exist in a system for a short time.
• This means these types of faults clear themselves and
supply can be restored.
• In this case the autoreclosure restores the supply
automatically by being closed and improves service
reliability.
Autoreclosure

• Auto-reclosers are usually vacuum or SF6


breakers.
• They can be programmed to give up to four
trips, either instantaneously or time delayed
or both to suit the power system.
• The necessary energy for the opening and
closing springs is obtained from the power line
itself.
Autoreclosure

• Protective devices are installed in the network


to protect the network from damages which
may take place in abnormal cases, short circuit
etc.
• Major problem exists in dealing with transient
faults.
– For e.g. a tree branch that is blown off a tree
during windstorm and lands on the line may cause
a short circuit that could cause damage. However,
the fault will quickly clear itself as the branch falls
to the ground.
Autoreclosure

• Reclosers address this problem by further


dividing up the network into smaller sections.
• This means reclosers may be installed at each
branch. As the reclosers are installed at
smaller sections, they handle much less power
than the breakers at feeder stations and
therefore can be set to trip at much lower
power levels.
Autoreclosure

• A normal breaker could also be used for this role, but


because they are distributed geographically throughout
the grid, as opposed to being centralized at feeder
stations, resetting a breaker might take considerable
time and may be too costly because of the manpower
cost and travel cost.
• For this reason reclosers are used to automatically re-
connect after a brief interval. There is a strong
likelihood that the fault will be gone when the power is
restored. If the fault is still present, the reclosure opens
again.
Autoreclosure

• The control system for a reclosure allows a selected


number of attempts to restore service after adjustable
time delays.
• For instance, a reclosure may have 2 or 3 fast reclose
operations with a few seconds delay, then a longer
delay and one reclose.
• If the last attempt is not successful, the reclosure will
lock out and require human intervention to reset.
• If the fault is a permanent fault (downed wires, tree
branches lying on line etc.) the fault needs to be
rectified and then to reset the reclosure.
Autoreclosure

• Auto-reclosers are made in single-phase and


three-phase versions.
• The ratings of reclosers run from 2.4 to 38 kV
for load currents from 10 – 1200 A and fault
currents from 1 – 16 kA.

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