Arc Fault Detection


Arc Fault Detection


Arc fault detection – Conventional circuit breakers do not afford reliable protection against arc faults. That is because they are not designed to detect sudden dangerous arcs. They ensure protection against short circuits and overloads.

What is an arc fault detection device?

Arc Fault Detection Devices (AFDDs) are devices that protect specifically against arc faults. They automatically trip a circuit when they detect dangerous electric arcs.

They are compact, modular devices that are easily installed along with other protective equipment. Each AFDD is designed to protect an electric, instantly detecting any dangerous arc. You should install AFDDs on the electrical circuits most exposed to risk – e.g., the final circuits that supply socket outlets or lighting in loft spaces in thatched cottages.

Can arc fault detection devices distinguish between dangerous and working arcs?

Yes. Arc fault detection devices are extremely sensitive and designed to sense and respond only to potentially dangerous arcs. They use a special algorithm to distinguish between dangerous and working arcs – i.e., the harmless sparks that you see when you flick a switch or pull a plug.
This is important as over-sensitive AFDDs could be prone to nuisance tripping – e.g., interrupting a circuit when it senses the slightest harmless arc.

How do arc fault circuit breakers work?

AFDDs constantly monitor and analyse patterns in electrical current and voltage waveforms. They are on the look-out for the random, non-predictable yet persistent patterns of waveform that denote a potentially dangerous arc.

When it senses a potentially dangerous wave pattern, it trips, thus isolating the faulty circuit. An AFDD can work in conjunction with a “circuit-breaker” or residual-current circuit breaker with overload protection (RCBO). It may also incorporate its own switching function.

AFDDs react very fast to the slightest change in wave patterns. Speed is of the essence as an electrical arc can degrade in a flash (literally), igniting any nearby inflammable material and causing a fire.

If you would like more information on Arc fault detection, please feel free to call JCE Contracting on 01373 455 690 or email