AFDD
Arc Fault Detection Device

Closes the gap between residual current circuit brea­kers and miniature circuit brea­kers.
An AFDD will trip the circuit when a pote­nt­i­ally hazardous arc occurs, elim­in­ating the resulting fire hazard.

What is the role of AFDD?

The arc fault detection device AFDD (also called arc fault prot­ection device) monitors serial and parallel arcs. Serial arcs occur e.g. B. by loose contact points that are in series with the consumer (supply and return conductor). If the fault current is high enough, a miniature circuit breaker can switch off in the event of a flas­h­over between the phase conductor and the neutral conductor, but the fire prot­ection switch already reco­g­n­izes the characte­ristic current and voltage curves from 2.5 amperes. The parallel arcing faults between L and PE ment­i­oned above can be detected and switched off in equal measure by AFDDs and FIs. This means that there is very good fire prot­ection with redundancy, provided that both machines monitor the same circuit.

Typical causes of arc faults

The graphic is inte­nded to give you a brief overview of faults that lead to arcing faults, which in turn can cause fires. Virt­ually anyw­here there is damage to live wiring that does not break the circuit, an arc can occur that can then set surro­unding mate­rials on fire.

Some errors, such as cable damage caused by dril­ling or cable kinks/cable breaks, occur immed­i­ately and can somet­imes be easily ident­i­fied and rect­i­fied. Other errors only develop over time and are usually not directly notic­e­able.


A term­inal point, for example, is not usually subject to constant testing. Tempe­rature-related expan­sion and corrosion can loosen contact with the cable. An arcing fault can occur over the resulting gap. Cable wear, in turn, is caused by frequent use and improper hand­ling of lines and cables. Alth­ough damage can be detected here, expe­ri­ence shows that devices with defective cables are often still in use because the people who use these devices are not suff­ic­i­e­ntly aware of the resulting dangers.

How does it work?

The key is in monito­ring the sine waves of current, voltage and 120 other param­eters. The characte­ristic current and voltage curves are rele­vant from a value of 2.5 A. The fire prot­ection switch has no physical triggers. The micro­p­roc­e­ssor elect­ro­nics within the AFDD in connection with the software algo­rithm detects a fire-trigge­ring energy content from a thre­s­hold value of > 450 J and switches off. 450 J is enough to set PVC cables on fire.


In an intact circuit, the param­eters are only brought into ranges that trigger the AFDD in exce­pt­i­onal cases. So-called operating arcs are able to influence the sine waves in such a way that they have a wave­form similar to an arc fault. These arcs form, for example, in the brush spark of a drill and in elect­ronic comp­o­n­ents and even light switches that cause arcs when switc­hing. However, the AFD units from Hager are able to dist­in­g­uish between operating arcs and fault arcs and only switch off in the event of a fault.

Practical information for your daily work

Insu­lation test acco­rding to DIN EN 61439

The test voltage is applied to the feed term­inals of the LV switc­hgear combin­ation. For test voltages:

  • ≤ 400 V the AFDD must be switched off (DIN EN 61439-3)
  • > 400 V the AFDD must be disc­o­n­n­ected (DIN EN 61439-2)

Insu­lation test during E-Check

If, for practical reasons, it does not make sense to disc­o­n­nect elect­rical equi­pment, the DC measurement voltage for the circuit can be reduced to 250 V. However, the insu­lation resistance must be at least 1MΩ (acco­rding to DIN VDE 0100-600).

Loop Impedance Measurement

If a loop impedance measurement acco­rding to DIN VDE 0100-600 is carried out on an outg­oing circuit with AFDD, the residual current caused must not exceed 300 mA.

Self-test repl­aces the funct­i­onal test

In cont­rast to the FI switch, no funct­i­onal test is nece­s­sary with our new fire prot­ection switch. The inte­g­rated micro­p­roc­e­ssor carries out a self-test at regular inte­rvals - as stip­u­l­ated in the product standard.

Infeed below, outlet above

We have improved the new AFDD gene­ration to make it even easier for you to install: The feed is at the bottom of the AFD unit, the outlet is at the top – as is gene­rally the case. Thanks to the tried-and-tested quic­kc­o­n­nect techn­o­logy, time-cons­uming scre­wing is no longer nece­s­sary and you can comp­lete your work in less time.

Phase busbars make instal­lation easier

With the new phase busbars, you can easily connect mult­iple arc fault prot­ection devices next to each other.

Standard and applic­ation

What does DIN VDE 0100-420 regu­late?

DIN VDE0100-420 regu­l­ates the use of measures to protect against the thermal effects of arcing in final circ­uits.

 

How do you prevent fires that can be caused by arcing faults?

Further details can be found simply and in summary on our information page on the DIN VDE0100-420 standard.

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