Auto-Recloser Demonstration Model for Distribution Feeders

Most faults on overhead distribution lines are transient — a lightning surge, a branch brushing the conductor, a bird across phases — and they clear themselves within a fraction of a second. Tripping the feeder and leaving it dead for a manual patrol would punish every customer for a fault that no longer exists. The auto-recloser exists for exactly this: it trips on fault current, waits a short dead time, and recloses automatically. If the fault has gone, supply is restored in seconds; if it persists, the recloser tries again a set number of times and then locks out, leaving the faulted section dead for the crew. This project models that behavior on a bench panel. A contactor plays the reclosing breaker; a timer-relay sequence implements trip, adjustable dead time, and reclose; a counter tracks the shot number; a toggle selects transient or permanent fault; and lamps plus a single-line mimic show RUN, FAULT, RECLOSE and LOCKOUT states. The student injects faults and watches the full sequence play out — including the difference a permanent fault makes.

1. With the feeder healthy, the breaker contactor is closed and the green RUN lamp glows; the shot counter reads zero.
2. The student presses the fault-injection button, simulating a fault on the feeder — the trip logic opens the breaker and the FAULT lamp lights.
3. The dead-time timer starts counting; the panel is quiet except for the FAULT lamp while the set dead time elapses.
4. At dead-time expiry the logic issues the first reclose: the contactor closes and the RECLOSE lamp flashes. With the toggle on transient, the fault has cleared and the unit returns to RUN, resetting the counter.
5. With the toggle on permanent, the fault is still present — the unit trips again immediately, waits the dead time, and recloses a second and third time, the counter advancing each shot.
6. After the third unsuccessful reclose the logic drives to LOCKOUT: the breaker stays open, the LOCKOUT lamp lights, and only the manual reset button can re-arm the unit.
7. The student repeats the sequence with different dead-time settings and records the observed timing for the report.

Tech stack:

• Auto-reclose protection theory
• Breaker trip and close control
• Timer relay logic
• Reclose sequence design
• Fault simulation
• Status indication circuits
• Feeder single-line diagrams
• Electrical panel wiring

• [Reclosing breaker model] A contactor rated for the model feeder acts as the reclosing breaker, with its coil driven by the trip/reclose logic.
• [Adjustable dead-time timer] The dead time between trip and reclose is settable from 1 to 10 seconds (design), so the student can observe its effect on the sequence.
• [Three-shot attempt counter] A digital counter tracks reclose attempts; after the third unsuccessful reclose the logic drives to lockout.
• [Fault injection with transient/permanent toggle] A push button injects the fault, and a toggle selects whether it clears itself (transient) or stays (permanent) — the two cases the recloser discriminates.
• [Lockout indication] A dedicated lamp and a manual reset push button reproduce the lockout-and-reset behavior of real units.
• [Feeder single-line mimic] A labeled mimic diagram with LEDs shows the feeder, breaker state and fault point, so the sequence reads like a control-room panel.
• [Status lamps] RUN, FAULT, RECLOSE and LOCKOUT lamps make every logic state visible at a glance.

• Bench panel with reclosing breaker contactor, timers, counter and lamps
• Fault-injection button with transient/permanent selector
• Feeder single-line mimic diagram with LED indication
• Manual reset and dead-time adjustment controls
• Wiring and schematic diagram of the trip/reclose logic
• Project report PDF (background, recloser theory, sequence analysis, observations)
• PPT presentation for final review
• Viva Q&A preparation document (dead time, shots, lockout, transient vs permanent)

• This is a low-voltage bench model; real auto-reclosers are pole-mounted medium-voltage devices with vacuum interrupters.
• The breaker is a contactor, not a vacuum interrupter — actual arc interruption physics is not demonstrated.
• Dead times are in seconds for classroom observation; real reclosers operate in cycles.
• Permanent-fault discrimination is simplified to the toggle; real units use fault-current and sequence-coordination logic.
• The model demonstrates protection logic only — it is not field equipment and is not rated for any real feeder duty.