The Arc Flash can be initiated through accidental contact, equipment which is underrated for the available short circuit. current, contamination or tracking over insulated surfaces, deterioration or corrosion of equipment and, or parts, as well. as other causes.
https://www.geindustrial.com/sites/geis/files/gallery/The-Basics-of-Arc-Flash-Article_GE_Industrial_Solutions_0.pdf
Unsafe arc faults can occur as series or parallel arcs. A series arc can occur when the conductor in series with the load breaks. The series configuration means the arc current cannot be greater than the load current the conductor serves. Typically, series arcs don't develop sufficient thermal energy to create a fire. More dangerous is the parallel arc fault, which can occur as a short circuit or a ground fault.
http://ecmweb.com/content/basics-arc-fault-protection
The arc causes an ionization of. the air, and arc flash. temperatures can reach as high. as 35,000 degrees Fahrenheit. This is hotter than the surface. of the sun”. eardrums to rupture resulting in temporary or permanent hearing loss. Molten metal can be sprayed by the blast throughout the vicinity.
https://www.geindustrial.com/sites/geis/files/gallery/The-Basics-of-Arc-Flash-Article_GE_Industrial_Solutions_0.pdf
A ground fault parallel arc fault can occur only when a ground path is present. This type of arc fault can be cleared by a GFCI or an AFCI. The RMS current value for parallel arc faults will be considerably less than that of a solid, bolted-type fault. Therefore, a typical 15A breaker might not clear this fault before a fire ignites. UL 1699 contains the requirements for listing AFCI devices.
http://ecmweb.com/content/basics-arc-fault-protection
Most of us are familiar with an arc. The dictionary describes an electric arc. as “a luminous bridge formed in a gap between two electrodes”. An Arc Flash occurs during a fault, or short circuit condition, which passes. through this arc gap.
https://www.geindustrial.com/sites/geis/files/gallery/The-Basics-of-Arc-Flash-Article_GE_Industrial_Solutions_0.pdf
Sparking and arcing are exactly what the AFCI breaker is looking for, and so it will interrupt the circuit power. The engineers who have designed these AFCI Breakers found that motors, like the ones found in the power drill, vacuums and treadmills produce a rhythmic, mechanical arc pattern.
https://www.angieslist.com/articles/why-your-arc-fault-breaker-keeps-tripping.htm
The arc causes an ionization of the air, and arc flash. temperatures can reach as high as 35,000 degrees Fahrenheit. This is hotter than the surface of the sun. This kind of temperature can set fire to clothing and severely burn human. skin in fractions of a second at a significant distance from the event.
https://www.geindustrial.com/sites/geis/files/gallery/The-Basics-of-Arc-Flash-Article_GE_Industrial_Solutions_0.pdf
But at times, older products with motors will cause the AFCI breaker to trip. This is because the brushes wear down on these older motors, which causes the arc pattern to become irregular and not as rhythmic as when the motor was new. This causes AFCI to detect this as an arc and trip the circuit for safety.
https://www.angieslist.com/articles/why-your-arc-fault-breaker-keeps-tripping.htm
You may even recognize these arc-fault circuit interrupter breakers, with their visible TEST button in your circuit breaker panel. After having been slowly phased in over the past 3 NEC Code cycles, these new arc-fault breakers are now required on almost every 120V circuit in the finished space of the house.
https://www.angieslist.com/articles/why-your-arc-fault-breaker-keeps-tripping.htm
Ever wonder why your arc-fault breaker trips randomly? An electrician explains how arc-fault circuit interrupters work and what causes AFCI nuisance tripping. Anyone who built or did major renovations to a home over the last decade is probably familiar with the term arc-fault breakers, or AFCI breakers.
https://www.angieslist.com/articles/why-your-arc-fault-breaker-keeps-tripping.htm
what causes arc fault
An arc fault is caused when the conductor in series with the load breaks. When the conductor in series with the load breaks causes arc faults.