It is known that traditional circuit breakers only protect the overcurrent, short circuit and leakage, and the home Arc Fault Detection Devices (AFCI) I introduced today is a new function based on the traditional circuit breaker - protecting the fault arc, to prevent the fire caused by the arc. In the United States, according to the statistics of the CPSC (American Consumer Goods Safety Commission) in 1998, more than 40000 fires are caused by the aging of the electric arc caused by the aging of distribution lines, resulting in a direct economic loss of $16.8 billion. So CPSC requires all residential bedrooms to install such Arc Fault Detection Devices, and air conditioning to install AFCI sockets.

This paper will introduce the technology development of the circuit part of Arc Fault Detection Devices (AFCI), including its hardware and software implementation methods and related contents. We use a current transformer, sensing the size of the AC current and di/dt, and then using OP (OP AMP) processing, the signal is then input to the MCU for A/D processing, MCU to analyze the sampling value, if the characteristics of the fault arc, MCU will send off the circuit breaker off signal to break the circuit breaker. Of course, the traditional overcurrent, short circuit and leakage protection functions can be conveniently integrated, as long as an additional current transformer is added.

It is applied to all kinds of circuit breakers, wall outlets and power plug plates.

Basic concepts:
Arc:
There are two kinds of arcs on the circuit, one is the normal operation arc, the other is the arc fault.
1. "Good arc" refers to the arc generated by the rotation of electric motors, such as electric drills, vacuum cleaners, etc. In addition, when people switch electrical appliances, plug the electrical appliances, the arcs generated are also good arcs.
2. "Bad arc" are fault arcs. The types of fault arcs can be classified into two categories. Class A and B class. Class A is called series arc, and B type arc.