6 ELECTRIC.IE • The Magazine & Website for the Irish Electrical Industry • WHOSE FAULT IS IT? AFDDs An arc fault detection device (AFDD) is a safety device which activates in the presence of series and parallel arc faults by monitoring the waveform (signature) of an arc. It does this by electronically analysing the waveform and ‘trips’ when the waveform falls outside of predetermined values. The first Arc Fault Circuit Interrupter (AFCI) was patented in the US in 1980 and was described for use in the US National Electric Code (NEC) in 2008. In 2013 the Product Standard IEC 62606 was introduced and became a UK Standard that same year. IS EN 62606: 2013+A1: 2017 General requirements for arc fault detection devices states that the purpose of an AFDD is, ‘… to mitigate the risk of fire in final circuits of a fixed installation due to the effect of arc fault currents that pose a risk of fire ignition under certain conditions if the arcing persists’. Electric Arcs The phenomena of electric arcing were first demonstrated to the Royal Society in London by the chemist and inventor, Sir Humphrey Davy in 1801. Other studies followed and an electric arc can be considered to be: ‘An electrical breakdown of a gas that produces a prolonged discharge between two means of conduction’ There are instances where arcing is a desired effect, such as when welding or plasma cutting. However, uncontrolled arcing due to a fault is undesirable. Causes of arc Contact arcs can result from either direct or indirect contact between metal parts which are moving relative to one another or have little conductivity, such as a loose electrical connection or a break in conductor. To generate an arc is a complicated process, but AFDDs have been getting a lot of attention following the publication of Amendment 1 in 2024 and the corrigendum in 2025 of I.S. 10101 in September 2024 (National Rules for Electrical Installations). Jake Green, Head of Technical Engagement with Scolmore Group which includes Click Litehouse, looks at the technologies associated with AFDDs. *All references to regulations are from I.S. 10101: 2020+A1:2024+Corrigendum 2: 2025 National Rules for Electrical Installations. - Click Litehouse
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