It is important to prevent the fire of electrical fires that are the highest in the fire hazard, and to prevent fires from becoming more "burning". The Arc Fault Detection Devices(AFCI), designed to prevent electrical fires at the beginning , was created.
Electrical fires mainly originate from: (1) "series arc" or "parallel arc" short circuit caused by poor contact or insulation damage of electrical lines (mostly carbonization of line aging); (2) Grounding (arc) failure caused by the damage of ground insulation of electrical lines; (3) Abnormal temperature rise caused by poor contact of electrical lines, improper arrangement of electrical equipment, overload. Among them, the arc short-circuit is not easy to be found the is primary cause of electrical fire prevention. The temperature of the arc exceeds 5,500 °C each time, the thermal particles emitted by high-intensity thermoelectric arc are accumulated through time to ignite insulating materials around the line, causing electrical fires.
The current value of the series fault arc is less than the rated current of the loop, and the current value of the parallel fault arc may be greater than the rated current, and the starting current of the household appliance is greater than the rated current. For the protection of two arc faults and the need to bypass the equipment to initiate the inrush current, the traditional thermomagnetic system (such as terminal overcurrent protection or leakage protection device) can not detect the fault arc current and identify the arc fault, failing to prevent electrical fires. According to statistics: China's fires caused by arc faults from 2005 to 2009 accounted for 51% of total electrical fires, and direct economic losses accounted for 36% of total fires.
The development and application of power distribution intelligent technology enables Arc Fault Detection Devices AFCI, which realizes arc detection and fault signal recognition, to achieve arc fault protection requirements and avoid electrical fires. The National Electrical Code (NEC) defines it as a device that provides arc fault protection by detecting arcing, by identifying arc characteristics, and cutting off the circuit.
The Arc Fault Detection Devices AFCI includes a general structure such as an operating mechanism, a contact system, a trip mechanism, a test button, a terminal block, a frame, and the like, and the characteristic structure further includes an arc detecting circuit and an arc fault electronic identification circuit (including a microprocessor) based on the PCB hardware. And preset protection algorithm to realize intelligent arc detection and fault arc recognition.