Arc Fault Circuit Breaker technology is a new circuit protection technology. Its main function is to prevent fire caused by fault arc. When arc fault occurs, because the current intensity is small, which is lower than the setting value of over-current protection widely installed in power system, especially in low-voltage distribution field, installing AFCI Circuit Breaker at the terminal of distribution line is a measure to discover the arc in time and cut off the circuit so as to effectively reduce the loss caused by arc.

Arc Fault Circuit Breaker (AFCI) is an intelligent circuit protector. AFCI Circuit Breaker can detect and identify fault arcs and normal working arcs in electric circuits, and prevent fire hazards caused by faulty arcs such as poor contact and poor insulation in electrical circuits. It has fault arc protection, overload protection, short circuit protection, overvoltage protection and surge suppression.

1. Necessity of Fault Arc Detection

The basic components of the electrical fire monitoring system include: electrical fire monitoring equipment, residual current electric fire monitoring detector and temperature measuring electric fire monitoring detector. The system can monitor the current, remaining current and temperature in the maintained line, and find out the hidden danger of electric fire in time to prevent the occurrence of electric fire. However, many severe fire accidents are only caused by faulty arcs below rated current or expected short-circuit current in the line. These risky arcs may occur in unreasonably designed or aging power lines, electrical plugs and household appliances with power lines, internal wiring harnesses or component insulation. When the fault arc breaks out, the maintenance devices such as leakage, overcurrent and short circuit on the line may not be able to detect or be unable to act swiftly to block the power supply, which is very easy to cause fire.

2. The main damage of fault arc is to cause fire.

The main damage of fault arc is to cause fire. When the fault arc breaks out, the central temperature of the fault arc is as high as 3000 C to 4000 C, and accompanied by metal melt splashing out. The high temperature and high heat caused by fault arc can ignite the insulating layer of the line easily, and if there is combustible near the fault point, it can also ignite the combustible material easily and cause the fire.

3. Several kinds of fault arcs that can not be monitored by electric fire monitoring system

(1) Ground fault arc
In short-circuit fire of electric line, the fire caused by grounding fault arc is much more than that caused by fault arc fire between live conductors. This is primarily because the probability of earthing fault occurring is much greater than that of short circuit between live conductors.
Because the current waveform will be distorted when the earthing fault arc occurs and the fault arc current is sometimes absent, the remaining current detectors can not accurately and reliably detect such faults.
(2) Series fault arc
Electrical connection points are the thinnest or most vulnerable links in electrical connection, mechanical strength and maintenance measures, which will directly lead to arc or heat, and then lead to electrical fire. AFCI Circuit Breaker can prevent this problem.
When series fault arc occurs in the line, the remaining current in the line does not change, which makes the electric fire monitoring system unable to monitor such fault arc.
(3) Parallel fault arc between live conductors
When the two cores of the electric circuit touch each other and short circuit, the cores melt into clusters before they are soldered. When the two molten metal clusters shorten and separate, the arc may be set up.
In the early stage of parallel arc erection, because the arc has great impedance and voltage drop, which restricts the fault current, the circuit breaker on the line can not act reliably in time and block the power supply, so that the arc continues to exist. Arc Fault Circuit Breaker can solve this problem.