A Method for Residential Series Arc Fault Detection and Identification

Because of electrical problems such as aging cables and loose connections, arc faults occur. Generating high temperature and discharging molten metal, arc faults finally lead to electrical fires. Every year such fires bring great loss and damage. It is identified that conventional protecting technique is unable to break a circuit in the situation when a brief arc fault occurs and the arc current is below thermal or instantaneous trip levels. The paper describes how experiments on series arc faults (defined in UL1699) are performed. Then waveforms of arc faults in circuits with purely resistive loads are contrasted to those with inductive loads of different power factors. They are different especially on the 'shoulders' and the rising edges followed, which are analyzed both in time and frequency domain. Similar waveforms of normal working household appliances like air conditioners and computers, which have special characteristics, are also studied in the paper. Although the waveforms of computers are not easily distinguished from those of arc faults, it is found that the harmonic components of them are different. A method combining DFT and DWT, which is relatively simple, reliable and easily performed in Arc Fault Circuit Interrupters, is proposed to identify hazardous arc from normal waveforms.