AFDD fault arc protector

The invention provides an AFDD fault arc protector which comprises a power module, a CPU core module, a current sensing resistor module, an arc current signal processing module, a pulse processing module and a trip processing module. The power module is used for reducing the voltage in a turnover mode and making the L-phase end of a mains supply as a reference voltage reference point GND of a built-in system power supply. The CPU core module is used for processing received signals. By means of the AFDD fault arc protector, miniaturization of a built-in power supply system is realized, a traditional current transformer is not needed for arc current sampling, and arc current signals are collected directly from a strong current circuit; as a result, the AFDD fault arc protector is low in cost, small in size, low in mass, free of flux saturation, higher in cost performance, free of limitation of product sizes and capable of testing small arc currents and large arc currents at the same time; besides, the accuracy is within the range of 5%.