Most people know circuit breakers and fuses. Quite many also know ground fault circuit interrupter (GFCI) or Residual Current Device (RCD). But now a new protective device is coming to use in Europe and you might want to learn about it. AFDD/AFCI Arc Fault Protection Device protects people and property against fires caused by arc flashes. An arc-fault circuit interrupter (AFCI) also known as an arc-fault detection device (AFDD) is a circuit breaker that breaks the circuit when it detects an electric arc in the circuit it protects to prevent electrical fires.
AFCI breakers have been required for circuits feeding electrical outlets in residential bedrooms by the electrical codes of Canada and the United States since the beginning of the 21st century; the U.S. National Electrical Code has required them to protect most residential outlets since 2014.The electronics inside an AFCI breaker detect electrical current alternating at characteristic frequencies, usually around 100 kHz, known to be associated with wire arcing, which are sustained for more than a few milliseconds. As of January 2008, only “combination type” AFCIs meet the NEC requirement. The downsides of AFCIs are that they do not protect against all kinds of faults and AFCIs are also known to be sensitive (false tripping) to the presence of radio frequency energy.
Now the use of AFDD is also noted and recommended on Europe. The international standard IEC 60364-4-42:2010+A1:2014 and European standard HD 60364-4-42:2011+A1:2015 highly recommend using arc fault detection devices and consider them as the state-of-the-art devices in this area. According to IEC 60364-4-42 the installation of arc fault detection devices (AFDDs) is strongly recommended in many applications. The device is expected to attract particular interest from the residential sector. In the UK the 2018 edition of the wiring regulations is the first edition to make any mention of arc fault devices, and indicate they may be installed if the design has an unusually high risk of fire from arc faults.
AFDD is available as separate protective device and also as arc fault detection circuit breaker (MCB + Arc Fault Detection unit) that fits into a standard electrical panel. Both are designed to disconnect power before an electrical fire starts.
Arc fault detection device (AFDD) – recommended acc. to IEC standard
Let’s dig deeper in what those AFDD devices are and how they work. AFDD device tries to detect high frequency patterns on an electrical circuit that indicate an imminent arc flash and activates a trip switch to eliminate the risk. An AFDD/AFCI needs to selectively distinguishes between a harmless arc (incidental to normal operation of switches, plugs, and brushed motors), and a potentially dangerous arc (that can occur, for example, in a lamp cord which has a broken conductor). AFDD is designed to protect against three types of arc faults: Series fault arcs (conductor break or loss of contact in series with a load), parallel fault arcs L-N and parallel fault arcs L-PE.
AFDD – Arc Fault Detection Device – Part 1
AFDD Arc Fault Detection Devices Additional Tests (Part 2)
AFDD Regulations in BS7671, Other Information (Part 3)
The Arc Fault Detection Device (AFDD)
Arc Fault Detector / Demonstrator
ABB AFDD testing
Finally let’s take a look inside.
AFDD open box