Arc Fault Circuit Breaker uses electronic technology to identify arc state, and fault arc detection is the key link of arc fault protection of Arc Fault Circuit Breaker. The study on arc and fault arc detection began in the late 1980s and early 90s in the United States. By means of light, heat, sound and electromagnetic characteristics of arc discharge, the main methods of arc detection and fault recognition are as follows:
(1) According to the characteristics of arc waveform, the arc fault can be identified by judging whether the current waveform derivative and the cumulative arc period exceed the set threshold.
(2) According to the high frequency energy mutation of the arc, the Arc Fault Circuit Breaker recognizes the arc by detecting the energy mutation of the high frequency part of the current signal, and identifies the arc fault by detecting the number of arc.
(3) High frequency wavelet transform: high frequency sampling of load current is used to calculate the non zero crossing discrete wavelet coefficients and to determine whether the threshold is satisfied with the zero crossing signal of low frequency current by Arc Fault Circuit Breaker.
(4) Fourier transform: Short-time Fourier transform (STFT) is used to analyze the changes of fundamental, odd and even harmonic components of the sampled signal, and to extract and judge the fault characteristics of series arc.
(5) Time frequency analysis: Arc Fault Circuit Breaker is based on the difference of time delay of the high and low pulses which reflect the sudden change of current, which is based on the time domain of higher than and below the threshold.
(6) High frequency signal contrast: whether the high frequency current produced by the periodical is distinguished from the normal switching arc, and whether the spectrum range is different from the common high frequency harmonic generated by the power electronic devices.
(7) Arc wavelength switching: the AFCI Circuit Breaker converts the ultraviolet light in the arc light to visible light, which is converted from the photoelectric converter to the trigger signal.