US What a recloser is
A recloser (also called an auto-recloser or automatic circuit recloser) is a circuit breaker built for overhead distribution lines that can close itself again after tripping. When it detects a fault, it opens to clear it, waits a short time and closes again. If the fault has gone, supply carries on as normal. If the fault is still there after a set number of attempts, the recloser locks out and stays open, isolating the line beyond it.
The reason for reclosing is that most faults on overhead lines are temporary: lightning, a bird or squirrel, or a branch blown against a conductor for a moment. Once the arc is interrupted the fault often clears by itself. A recloser deals with these without a long outage and without sending a crew, and limits a permanent fault to the section beyond it. Reclosers are standardized under IEEE C37.60 and IEC 62271-111.
How a recloser works
A recloser contains a vacuum interrupter that opens and closes the circuit, current sensors on each phase, and a control that decides when to trip and reclose. A typical operating sequence runs like this:
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Detect. Current above the pickup setting tells the control there is a fault on the line beyond the recloser.
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Fast trip. The first one or two trips are fast, to clear temporary faults before downstream fuses have time to blow.
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Reclose. After a dead time, often from under a second to several seconds, the recloser closes again to test the line.
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Delayed trips. If the fault returns, later trips are slower, giving a downstream fuse time to blow and isolate a smaller section.
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Lock out. After the set number of operations, commonly up to four trips, the recloser stays open until it is reset remotely or by a crew.
Recloser vs circuit breaker, sectionaliser and fuse
Reclosers work alongside other protective devices on a feeder, and each has a different job.
| Device | Interrupts fault current? | Recloses automatically? | Where it sits | Main role |
|---|---|---|---|---|
| Recloser | Yes | Yes, built in | On a pole along the feeder, or at the substation | Clear temporary faults and isolate permanent ones |
| Circuit breaker | Yes, at higher fault levels | Only with a separate reclosing relay | In the substation | Protect the whole feeder from the source end |
| Sectionaliser | No | No | On a pole downstream of a recloser | Count the recloser’s trips and open while the line is dead |
| Fuse | Yes, once | No, it must be replaced | On spur lines and transformers | Isolate a small branch at low cost |
Coordinating these devices is a core part of protection design. In a fuse-saving scheme, the recloser’s fast trips clear a temporary fault before the fuse blows; in a fuse-blowing scheme, the fuse is allowed to clear the fault first so fewer customers see the interruption.
Types of recloser
Reclosers are grouped by how many phases they switch and how they are controlled. Single-phase reclosers protect single-phase spur lines. Three-phase reclosers trip all three phases together, which suits lines feeding three-phase motors. Triple-single reclosers can trip one phase at a time and lock out all three when needed, so a fault on one phase does not interrupt customers on the other two. Older reclosers used hydraulic control and oil interruption; current designs use vacuum interrupters with solid insulation and an electronic control, typically rated for the 15, 27 or 38 kV classes.
The recloser control
Modern reclosers are paired with an electronic recloser control in a cabinet lower down the pole. The control holds the protection settings and sequence, records fault events and load data, and communicates with the control room over radio, cellular or fiber using protocols such as DNP3 or IEC 60870-5-104. That link lets operators see the recloser’s state, change settings and trip or close it remotely, and makes the recloser a building block of feeder automation.
Alongside the dedicated control, many sites add a small computer in the cabinet to run automation logic, gateways or monitoring software. It has to cope with the same conditions as the control: no heating or cooling, wide temperature swings and electrical noise from the switchgear. Our distribution automation case study covers the fanless computers used in those cabinets, and fanless DIN rail PCs clip onto the same rail as the control’s terminals. Our industrial temperature range FAQ explains the ratings they need outdoors.
Quick answers on reclosers
Reclosers: common questions
What does a recloser do?
It clears faults and restores supply automatically. It trips on fault current, recloses to test whether the fault has gone, and locks out only if the fault is permanent.
What is the difference between a recloser and a circuit breaker?
A recloser has reclosing built in. A substation circuit breaker needs a separate relay to reclose, handles higher fault currents and usually protects the whole feeder, while a recloser sits out along the line.
How many times does a recloser try?
Usually up to four trips. A common setting is two fast and two delayed operations before lockout, but the number and timing are set by the network operator.
Why do my lights flicker off and on during a storm?
Often a recloser at work. Each brief blink is the recloser tripping and closing again to clear a temporary fault. If the power then stays off, the recloser has locked out.
What is the difference between a recloser and a sectionaliser?
A sectionaliser cannot break fault current. It counts the upstream recloser’s operations and opens while the line is dead, isolating the faulted section.
We supply fanless DIN rail and wide temperature computers for recloser cabinets and feeder automation with the serial, Ethernet and cellular modules fitted as standard, and test each system before it ships. Tell us what the computer connects to and where it is mounted, and we will specify the build to match.