Technology status of AFCI Circuit Breaker
AFCI Circuit Breaker uses electronic technology to identify arc state, and fault arc detection is the key link of arc fault protection. 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 of AFCI Circuit Breaker are as follows:
(1) According to the characteristics of the arc waveform, the arcing fault can be identified by judging whether the derivative of the current waveform and whether the accumulated arc period exceeds the set threshold.
(2) According to the high frequency energy mutation of the arc, the arc is identified by detecting the energy mutation of the high frequency part of the current signal, and the arc fault is identified 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.
(4) The Fourier transform is used to analyze the characteristics of the series arc fault by analyzing the fundamental and odd and even harmonic components of the sampled signal by the short time Fourier transform.
(5) Using time-frequency analysis: Based on the difference of the time delay time between the high and low pulses reflecting the sudden change of current, the time domain which is higher than or below the threshold is used as the basis of judgement.
(6) Using 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 is used to transform the ultraviolet light from the received arc light into visible light and convert the photoelectric converter into trigger signal.