Power Distribution and Management

Do you know an Arc Fault Detection Device (AFDD) can prevent from an electrical fire?

Rome’s Fiumicino airport fire. Courtesy of ABC News

Conventional circuit breakers do not provide reliable protection against arc faults. That is because they are not designed to detect sudden dangerous electrical arcs, but do ensure protection against short circuits and overloads.

And even if you are careful to keep cords out of harm’s way and to use only certified plugs and adapters, arc fault conditions may build up out of sight. In most buildings power use alternates between periods of peak and standby consumption. Such patterns put a strain on cables and connections, wearing out the insulation and loosening wires. As a result, weak points form in your installation. That’s where electrical arcs occur.

And you have no way of knowing, until it’s too late. Unless, that is, you have an arc fault detection device.

What is an arc fault detection device?

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

They are compact, modular devices that are easily installed into electrical panels along with other protective equipment. You should install AFDDs on the electrical circuits most exposed to risk – e.g., the final circuits that supply socket outlets.

Electrical Safety GuideCan 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 analyze patterns in electrical current and voltage waveforms. They monitor for the random, non-predictable yet persistent patterns of waveforms 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 quickly 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.

Why aren’t AFDDs a standard requirement?

Since 2013, Arc Fault Detection Devices are covered by IEC 62606. This international standard defines the safety aspects of the AFDDs, and defines their operating characteristics.

Please feel free to post your comments and questions on this new technology. Visit our site to learn more about electrical safety.

43 Responses
  1. Leghnider

    hello Jean-Francois, thanks for your extended explanations.

      • Carly Freitas

        According to IEC standards for Arc Fault Detection Devices (IEC 62606) and to International Installation Standards (IEC 60364), AFDD are intended to protect one final circuit, and the shall be installed at the origin on the final circuit to be protected.

        Jean-François Rey

  2. subrata deb

    What will be the wave shape of voltage & current during arc fault? Will be the current more resistive? Number of sample measurement to confirm persistent arc .Appreciate if you can furnish detail technical literature.
    What will be the price if marketed in India?

  3. Jean-Francois Rey

    In case of arc fault in serie with the load, the voltage across the arc is constant voltage (typical arc voltage is from10 to 40 V), and the voltage across the load is decreased in consequence. Therefore, if the load remains unchanged, the current through the load will decrease according to the reduction of the voltage. The waveshape of the current will show “shoulders”, because when the instantaneous voltage is smaller than the arc voltage, current cannot flow in the load. The oscillogram attached shows typical waveshape of voltage and current, as described in future IEC 62606, and measured in laboratory conditions.

    However, you also have to consider that an arc is not a stabilized phenomena, therefore, the detection of arcs in AFDD shall also take into account high frequency features, duration of the arc, sustainability, and many other parameters. For example a small arc in a switch when you switch ON or OFF is not dangerous, however a maintained arc in an installation can spark a fire.

  4. Gordon

    Thank you for your explanation. Searching AFCI on internet I notice that in US they are available in two shapes, breaker and included in socket outlet. What is the difference and when I have to use one instead of the other?

    • Ed Larsen

      In the US, circuit breaker type AFCIs and outlet branch circuit type AFCIs (socket type AFCIs) must meet the same performance requirements. The difference is where they are located in the branch circuit. Circuit breaker type AFCIs have the ability to protect the entire branch circuit and the cords plugged into the sockets in the branch circuit. An outlet branch circuit type AFCI only have the ability to protect the cords plugged into it and the branch circuit wiring downstream from it. This would leave the wiring from the upstream panel to the outlet branch circuit type AFCI, commonly called the “home run” in the US, unprotected.

      The US National Electrical Code (NEC) requires arcing fault protection for the entire branch circuit, including the home run, so some other means of protecting the home run is required. The 2011 edition of the NEC allows the use of an outlet branch circuit AFCI if the home run is in a steel wiring method (conduit or armored cable) and the outlet branch circuit type AFCI is installed in a steel box or if the home run is encased in 50 mm (2 inches) of concrete.

      The preceding rules apply for new construction. If a branch circuit is extended or modified, either a circuit breaker type AFCI or an outlet branch circuit type AFCI is required to protect the branch circuit with out the steel wiring method or concrete encasement requirements.

      The 2011 NEC also requires that if a socket is replaced in a branch circuit that requires AFCI protection, then the replacement socket must be an outlet branch circuit type AFCI or the circuit must be protected by a circuit breaker type AFCI. This rule is effective January 1, 2014.

  5. Vinod


    Thanks for the interesting information about these protective devices. I have two questions ,is it mandatory for households in Europe to have these AFDDs installed and does Schneider Electric already have these AFDD`s out in the market.

    • Jean-Francois Rey

      Installation of AFDD in household and similar applications is being discussed in International Standardization Committees (IEC 60364). Due to the importance and consequences of fires in dwelling, IEC may require AFDD in the most critical cases.
      Schneider Electric is in the process to prepare AFDD, in conformity with European Standard EN 62606, it will be proposed to our customers in the coming months.

  6. Jorge


    Is there any scheneider-electric commercial AFDD in industrial applications for preventing the maintenance workers for the consequences of any possible electric arc while working?

    Thanks in advance

  7. Jean-Francois Rey

    Hello Jorge,
    AFDD (Arc Fault Detection Device) is a device intended to mitigate the risk of fire in final circuits of a fixed installation due to the effect of persistent arc fault currents, according to international standard IEC 62606. AFDD are known in the USA as AFCI (Arc Fault Circuit Interrupter) and comply to UL 1699. AFDD (and also AFCI), are not intended to for preventing the maintenance workers for the consequences of any possible electric arc while working.

    If you would like to prevent the maintenance workers for the consequences of any possible electric arc while working, you should use devices known as Arc Flash Devices. (know more here: > https://www.schneider-electric.com/products/ww/en/4700-protection-relays-by-range/4765-vamp-protection/62049-vamp-arc-protection-relay-system/)

  8. Paul Ralston

    Nice mode Schneider. You have a great product for new build, but with a with of 4 x 9mm din width, it won’t encourage retrofit in the existant housing stock (I live in France). How long become you fan miniaturise it to be 18mm wide to replace a régular 2xpole disjoncteur?

    • Jean-Francois Rey

      Hi Paul,

      You are right, not so easy to replace an existing 18mm MCB with a AFDD 36mm width
      How long to miniaturize? It depends how long the market will take to recognize this new protection as a mandatory one.
      Anyway, if you want to add AFDD without modifying deeply you MCB cabling, you can also add an AFDD in series with existing MCB of fuses, if you still have some space in your switchboard., of course.

      Let me know if you have more questions.

  9. Mike

    Can a socket or lighting be protected with RCD and AFDD ? If yes, in what order ( upstream/downstream) ?

    • Jean-Francois Rey

      Hi Mike,

      According to IEC 60364-4-41 (2005) , it is mandatory to protect the circuits supplying socket outlets by a RCD (Residual Current Device). The RCD shall have a residual current operating current not exceeding 30 mA .
      The RCD shall be situated upstream the socket-outlet to be protected, and is generally located in the switchboard. An RCD may protect several final circuits.

      In addition, according to IEC 60364-4-42 (2014), it is recommended to protect the final circuits :
      – in premises with sleeping accomodations,
      – in locations with risks of fire due to the nature of processed or stored materials, i.e. BE2
      locations, (e.g. barns, wood-working shops, stores of combustible materials);
      – in locations with combustible constructional materials, i.e. CA2 locations (e.g. wooden
      – in fire propagating structures, i.e. CB2 locations;
      – in locations with endangering of irreplaceable goods.
      The AFDD shall be situated at the origin of the final circuit to be protected.

      An RCD can protect several final circuits whereas, an AFDD is only intended to protect one final circuit. That’s why usually RCD protection is upstream AFDD protection.
      In case the RCD protects only one final circuit (usually this is a RCBO : circuit-breaker + RCD), the AFDD (usually AFDD is associated with a circuit-breaker) that also protect the same final circuit can be situated either upstream or downstream.

      Let me know if you have more questions.

  10. Jonna

    Is the AFDD from Schneider available already? I could not find the correct product from your web site. If not, when should it enter the market?

  11. Jonna

    I have found an AFDD from the French webpage of Schneider Electric but not for other countries. When will be available elsewhere in Europe?

  12. Kevin Castel

    Hello Jonna. Thanks for your interest for this Product. AFDD may not yet available in your country. To know more about the availability of this products and others, I invite you to contact your customer care agent by phone or email: https://goo.gl/I9JTyE

    You can also download our new customer care app
    available on iTunes: https://itunes.apple.com/tc/app/customer-care-by-schneider/id714825126?mt=8
    and Google Play: https://play.google.com/store/apps/details?id=com.schneider.qrcode.tocase

  13. Steve Timss

    does a power cord equipped with an LCDI detect an arc on the line side or the load side (or both)?

  14. Anuj

    Dear Sir,
    I am planning to Buy Schneider ADS
    Could you pls give some references where you installed and suppliying this in Northern India.
    Waiting for your reply.

  15. Karl Atkin

    Hi there,

    How would you carry out fault diagnosis on a circuit tripping due to an arc fault?

    I.e RCD’s tripping due to earth leakage can be found carrying out insulation resistance tests between Line-Earth and Neutral-Earth etc.

  16. Jean-François REY

    Arc Fault Detection Device are devices intended to monitor the electrical installation and to detect if dangerous arc are present. If a dangerous arc is present, the AFDD switches off the incriminated circuit. AFDD requires powerful analytics to differentiate between a “normal” arc, e.g. a small arc occuring when switching ON and OFF a wall mounted switch, and a “dangerous” persistent arc that may initiate a fire in the installation. According to IEC 62606, AFDD detect both series arcs that are in series with the load and parallel arcs, which may occur between the power lines.

  17. Charlie McCluskey

    Thanks for the explanation – it’s looking increasingly likely these will be more common in the UK with the upcoming new regs (18th edition) in 2018 – hopefully the prices come down a bit too!

  18. Colm O Duill

    I’m still not sure how this differentiates between required variations in a circuit with load and potentially dangerous arching. Regardless, can you say that by installing a AFDD it will cut out the risk of a fire from arching? Installing in a movie studio environment?

  19. Coralie Ogden

    Brilliant information please continue to publish further electrical information

  20. Matthew McKaig

    Does the AFDD work when excess resistive heat is the main culprit – so not arcing as the source of excess heat?

    • Ashley Baker

      “According to IEC 62606, AFDD are intended to detect dangerous arcs that may create fire in the electrical installation. A hot point in an electrical connection will, in general, create an arc, and this arc will be detected by the Arc Fault Detection Device.” — Jean-François REY

  21. Alan Fitchett

    Is it true these devices work well on radial circuits but not as good on Ring circuits?
    If so why

    • Jean-Francois Rey

      Dear Alan,
      In ring final circuits, an AFDD will afford the protection against dangerous arcs
      In the event of a break in a leg of a ring final circuit, the load current will flow through the resulting radial circuits therefore, the risk of fire hazard due to series arcing is negligible.

      See also the following useful booklet from BEAMA – https://www.beama.org.uk/asset/0C5A2A43-C78C-40A5-98513C9F6CCB343F

  22. Cliff Hammans

    Will manufacturers have these devices as standard on domestic consumer units for the implementation of the 18th Edition regs for Ist Jan 2019 . Also , I assume a new tester/meter will be needed to check AFDD compliance ,which will need to be recorded on new certification .

    • Jean-Francois Rey

      AFDD will be available on the UK market 2019/Q1, as this is a recommendation from the new edition of BS 7671. As for testing of such devices, the test button, present on the device, allows a simple verification of correct behaviour of the AFDD.

  23. James Raby

    Hi, thanks for the informative blog post! I’m seeing a lot of confusion after the introduction of the 18th edition (mainly relating to pricing!) but a question I have is are there ever likely to be single module AFDDs? We do a lot of domestic & light commercial works and some of the consumer units are tucked away in cupboards/etc…

    This makes consumer unit overall size an important factor as quite a few of our previous installations certainly wouldn’t have been able to fit the size of board that is going to be required with AFDDs (not to mention SPDs).

  24. James Raby

    Hello I came across your blog whilst searching for more information about AFDDs following the recent changes to the wiring regulations here in the UK.
    Your blog post has answered a lot of the technical queries I had, however the cost of these devices is still a thorny subject for many customers. Indeed we have some customers where replacement of the distribution board will now cost into the £thousands should AFDDs be fitted.

    Obviously as a responsible electrical contractor we want to ensure our customers electrical installations are both compliant and safe, however these costs are putting off the customers from upgrading in the first place (which sort of has a negative overall effect on safety!)

    I’m not here “price seeking” but am wondering if the cost of these devices is likely to come down once we have had them in the UK for some time?

    • Jean-Francois Rey

      AFDD is today new technology, with adoption in countries, such as Germany, Austria and UK.  This technology will be for sure more and more adopted and devices more and more sold, this will drive AFDD to become more accessible.

    • Jean-Francois Rey

      As technology becomes adopted and devices more and more sold, the product will become more accessible.

  25. Richard

    dear Sir,
    will AFDDs 32A and 40A be available too?
    If not, what is your recommendation for protecting socket outlets circuits ?

  26. Sergey

    Hello Jean-Francois! Can you please tell me if these devices are delivered to Russia? Is the question of applying this type of protection in medium voltage networks 6-20 kV considered?

    • Jean-Francois Rey

      Dear Sergey,
      Please note that AFDD is intended to protect against dangerous series and parallel arcs which may occur on Low Voltage Final Circuits, and initiate a fire. AFDD is not a device intended to be used in HV systems. 
      AFDD are not commercialized on the Russian market yet.