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The problem
An arc flash — the explosive release of energy when an arc fault strikes inside switchgear — can reach thousands of degrees in milliseconds, and conventional overcurrent relays with their inverse-time curves simply cannot clear it fast enough to limit the damage. Dedicated arc-flash protection relays solve this with a different signature: they watch for the blinding light of the arc with optical sensors and confirm with overcurrent, tripping in a few milliseconds because light arrives long before current-time curves would act. This project builds that protection concept as a safe student demonstrator: a model switchgear panel fitted with zoned optical arc sensors and a current transformer, a high-speed controller implementing light-plus-current trip logic, and a demo shunt-trip breaker as the trip target. A high-intensity LED arc simulator provides the "arc" for testing — no real arcing is ever created — so the speed and selectivity of optical detection can be demonstrated and measured safely on the bench.
Point photodiode modules watching the panel zones.
Follow the working sequence
How it works
- The optical sensors watch their panel zones continuously; their signals feed fast comparators with an adjustable light threshold.
- A current transformer on the demo feeder measures load current; its signal feeds an adjustable overcurrent threshold stage.
- Under normal conditions neither threshold is crossed; the controller holds the trip output and runs sensor supervision in the background.
- The LED arc simulator fires a high-intensity pulse into a zone while the test load draws overcurrent — the arc-plus-fault signature.
- With light AND current thresholds crossed together, the controller issues the trip within its design-target time, driving the shunt-trip contactor open.
- The zone LED latches to show which sensor saw the arc, and the event is time-stamped into the log.
- Light without current (simulated flash) or current without light (plain overload) produces no trip — demonstrating the supervision logic; a manual reset restores the demo breaker.
Tech stack:
- High-speed microcontroller (trip logic, supervision, event logging)
- Point optical arc-light sensor modules (photodiode-based, fiber-coupled option)
- Fast comparator stage for the light threshold
- Current transformer with burden resistor and overcurrent threshold stage
- Shunt-trip contactor as the demo breaker
- High-intensity LED strobe arc-light simulator
- Zone LEDs and LCD for event display
- Firmware in C/C++; oscilloscope timing-measurement procedure
| Parameter | Value |
|---|---|
| Detection principle | Optical arc light + overcurrent supervision |
| Trip time | Design target <10 ms light-to-trip-contact (component-derived) |
| Sensor zones | 2–3 point optical sensors with zone indication |
| Current supervision | CT-based, adjustable overcurrent threshold |
| Trip output | Shunt-trip contactor drive (demo breaker) |
| Arc simulation | LED strobe arc-light simulator (safe, no real arcing) |
| Supervision | Continuous sensor health/fault monitoring |
| Event recording | Time-stamped trip log on LCD |
Project features
- [Optical arc sensors] Point light sensors (photodiode modules, fiber-coupled option) watch the zones of the demo panel, shielded and filtered against ambient light.
- [Light-plus-current trip logic] A trip issues only when intense arc light AND overcurrent coincide — the industrial supervision principle that stops camera flashes or switching transients from causing nuisance trips.
- [High-speed trip output] Design-target sub-10 ms from light detection to trip contact (derived from sensor, comparator and controller delays), driving a demo shunt-trip contactor.
- [Zone-selective sensing] Two to three sensor zones with individual zone LEDs identify which panel zone saw the arc — the basis of selective tripping discussions.
- [Safe arc simulator] A high-intensity LED strobe module simulates arc light for testing and timing measurement; no real arc flash is ever produced.
- [Sensor supervision] Continuous health checking flags a disconnected, blinded or failed sensor with a fault LED — supervision is part of real relay design.
- [Event log] Time-stamped trip and supervision events on the display give the report its test record.
What is included
- Demo switchgear panel with zoned optical sensors and CT
- Relay controller board with firmware (trip logic, supervision, logging)
- Shunt-trip contactor as the demo breaker
- LED arc-light simulator module
- Circuit schematic and wiring diagram
- Bill of materials with part numbers and sourcing notes
- Project report PDF (arc-flash background, light+current principle, buyer-run timing procedure)
- PPT presentation for final review
- Viva Q&A preparation document (arc flash, protection speed, optical detection, relay supervision)
- Setup and demo guide (simulator tests, timing measurement, safe operation)
Advantages
- Point optical sensors watch zones of the demo panel, shielded and filtered against ambient light, with a fiber-coupled option.
- A trip issues only when intense arc light and overcurrent coincide, the industrial supervision principle that stops camera flashes or switching transients causing nuisance trips.
- Zone-selective sensing across two to three sensor zones with individual zone LEDs identifies which panel zone saw the arc.
- A high-intensity LED strobe module simulates arc light safely for testing and timing measurement, with no real arc flash ever produced.
- Continuous sensor supervision flags a disconnected, blinded or failed sensor with a fault LED, and time-stamped trip and supervision events give the report its test record.
Disadvantages
- This is an academic demonstrator, not a certified protection relay, with no type testing or arc-flash containment certification, and it must never be presented as protection for real switchgear.
- It cannot be tested against a real arc flash in a student lab, so all timing and logic tests use the LED arc simulator.
- The sub-10 ms trip figure is a design target derived from sensor, comparator and controller propagation delays, not a calibrated measurement.
- The demo panel runs at safe low voltage, so sensor behaviour at real switchgear light levels and distances is discussed from literature, not demonstrated.
- Nuisance-immunity is demonstrated with simulated stimuli only, and qualified supervision is required for all powered testing of the panel and contactor.
Limitations & prerequisites
- Academic demonstrator, not a certified protection relay: it has no type testing, no arc-flash containment certification (e.g. IEEE C37.20.7 / IEC 62271 arc testing), and must never be presented as protection for real switchgear.
- It cannot be tested against a real arc flash in a student lab — all timing and logic tests use the LED arc simulator, and the report states this openly.
- The sub-10 ms trip figure is a design target derived from sensor, comparator and controller propagation delays, not a calibrated measurement; the report includes a buyer-run oscilloscope procedure to measure the actual time.
- The demo panel runs at safe low voltage; sensor behavior at real switchgear light levels and distances is discussed from literature, not demonstrated.
- Nuisance-immunity (light without current, current without light) is demonstrated with simulated stimuli only.
- Qualified supervision is required for all powered testing of the panel and contactor.
Frequently Asked Questions
Is this project suitable for a final-year project?
Yes — for Electrical Engineering programs. It demonstrates protection philosophy, high-speed sensing, light-plus-current supervision logic and relay testing practice, with measurable trip timing for the report.
Do you create a real arc flash for testing?
Never. A high-intensity LED strobe simulates arc light safely; real arc flashes are destructive events tested only in certified high-power laboratories.
Why light plus current, not light alone?
Light alone would nuisance-trip on camera flashes or switching transients; current supervision confirms a genuine fault. The demo proves both halves: each stimulus alone produces no trip.
Is the trip time measured or claimed?
Sub-10 ms is a design target derived from component delays. The report includes a buyer-run oscilloscope procedure so you measure and document the actual light-to-trip time on your build.
Can this protect real switchgear?
No. It is an educational demonstrator with no type testing or arc-containment certification; real installations use certified relays installed by qualified engineers.
What will I receive with the project?
The demo panel with sensors and CT, relay controller with firmware, shunt-trip contactor, LED arc simulator, schematics, BOM, project report PDF, PPT, viva Q&A and a setup/demo guide. Suitable for B.E./B.Tech final-year projects in Electrical Engineering.
Components & software requirements
- High-speed microcontroller (trip logic, supervision, event logging)
- Point optical arc-light sensor modules (photodiode-based, fiber-coupled option)
- Fast comparator stage for the light threshold
- Current transformer with burden resistor and overcurrent threshold stage
- Shunt-trip contactor as the demo breaker
- High-intensity LED strobe arc-light simulator
- Zone LEDs and LCD for event display
- Firmware in C/C++; oscilloscope timing-measurement procedure
Delivery information
Built-to-order project. Delivery timeline is shared after order confirmation based on current queue.
Support terms
Complete documentation, setup guide, and viva preparation included. Support for setup and explanation provided.
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Development of an Active Optical Lens for Arc Flashing Detection (Sensors, 2023)