Arc Fault Detection Devices

In­creas­ing Pro­tec­tion

Arc fault pro­tec­tion devices (AFDD) use mi­cro­pro­cessors to identify char­ac­ter­istic cur­rent flow and voltage curves that in­dic­ate an arc fault and auto­mat­ic­ally trip the af­fec­ted cir­cuit.

This sig­ni­fic­antly re­duces the risk of fire due to faulty con­duct­ors and con­nec­tions. The pro­tect­ive func­tion of the AFDD has already proven its worth in­ter­na­tion­ally, and has been used in Ger­many since Feb­ru­ary 2016.

The 18th edi­tion of BS 7671, when pub­lished in July, re­com­mends the use of these to provide ad­di­tional pro­tec­tion against fire.


Mon­it­or­ing via Mi­cro­pro­cessor

An AFDD is ac­tiv­ated by both series and par­al­lel arc faults. Un­like cir­cuit break­ers or RCDs, an AFDD does not have an elec­tromech­an­ical trig­ger, but util­ises elec­tronic tech­no­logy to ana­lyse the sig­na­ture (wave­form) of an arc. It re­li­ably dif­fer­en­ti­ates between an arc fault and the sig­na­ture (wave­form) in nor­mal switch­ing and con­trol events, pre­vent­ing false trip­ping.


Po­ten­tial Causes

Arc faults can be caused by all types of line faults and worn con­tacts;
  • Kink / break in a cable
  • Cable wear due to frequent use
  • Cable damage resulting from drilling or construction work
  • Incorrect wire stripping
  • Incorrect bending radii
  • Loose screwed connections
  • Defective wall plugs
  • Rodents biting cables

An AFDD will trip the cir­cuit when a po­ten­tially haz­ard­ous arc oc­curs, elim­in­at­ing the res­ult­ing fire haz­ard.


Ring Fi­nal Cir­cuits

Con­trary to com­mon be­lief, AF­D­D’s do of­fer pro­tec­tion against arc faults in ring fi­nal cir­cuits and to the equip­ment be­ing fed from this cir­cuit. A series arc fault in one leg however, is un­likely to be at a dan­ger­ous level so will not be de­tec­ted. This is due to cur­rent in this in­stance flow­ing around the other leg of the ring. A series arc fault will be de­tec­ted in equip­ment and in flex­ible cables con­nec­ted to the ring fi­nal cir­cuit. Par­al­lel arc faults are de­tec­ted and dis­con­nec­ted in all parts of the ring cir­cuit and on all con­nec­ted equip­ment.



What does AFDD stand for?

Arc Fault De­tec­tion Device.


Where do I need Arc Fault De­tec­tion?

AF­D­D's should be in­stalled in a loc­a­tion that is eas­ily ac­cess­ible. They pro­tect 120 volt, single-phase, 15- and 20-ampere branch cir­cuits sup­ply­ing elec­trical out­lets or devices that are in­stalled in kit­chens, liv­ing rooms, fam­ily rooms, re­cre­ation rooms etc.


How does an AFDD work?

AF­D­D's work by pro­tect­ing against arc faults when they in­stant­an­eously trip a cir­cuit when they de­tect elec­tric arcs. This pre­vents the pos­sib­il­ity of a fire oc­cur­ring.

What types of cir­cuits can AF­DDs be used on?

The reg­u­la­tions spe­cify that 230 volts ac fi­nal cir­cuits that in­clude ring cir­cuits, ra­di­als, spurs and more. 



Ef­fect­ive Areas Of Pro­tect­ive Devices De­pend­ing On Fault Po­s­i­tion & Type

Fault Between Short Circuit  Overload  Residual Current  Serial Arc  Parallel Arc 


Fur­ther In­form­a­tion

The Hager tech­nical team con­trib­ute to a num­ber of key in­dustry pub­lic­a­tions, for AFDD we have been in­volved in the pre­par­a­tion of the BEAMA Guide to Arc Fault De­tec­tion Devices (AF­DDs)




More from the 18th Edition

Surge Protection

A transient overvoltage or surge is a short duration increase in voltage measured between two or more conductors. In short this means anything from microseconds (millionths of a second) to a few milliseconds (thousandths of a second) in duration.

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Selection of RCD Types

RCD's exist in various different forms and react differently depending on the presence of DC components or different frequencies.

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Overload Protection

Devices such as switches, RCCBs etc. in distribution boards and consumer units may have historically had their rated current determined after having taken diversity into account but without having considered overload protection of the devices.

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BEAMA Guides

A collection of the latest guides relating to 18th Edition, Hager is proud to be a technical contributor to these guides which provide technical advice on a range of 18th Edition related topics.

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Related Products

Check out our product solutions for Arc Fault Detection below

Residential - Arc Fault Detection Devices


Commercial - Arc Fault Detection Devices


An AFDD solu­tion tailored for you

Our Arc Fault De­tec­tion Devices com­ply­ing with BS EN 62606 form the basis of our of­fer. However, when com­bined with our dis­tri­bu­tion sys­tems, provide a solu­tion which has been rig­or­ously tested and val­id­ated to of­fer op­timum pro­tec­tion against the harm­ful ef­fects of dan­ger­ous elec­tric arcs.

Engineered Solutions