| 摘要 |
<p>According to the present invention, in a switch inserted into a direct-current electrical path, magnetic variation around the electrical path is detected by a magnetometer. An extraction means extracts the signal of a frequency band in which "noise caused by arcing" can be easily determined based on the magnetometer output. An arcing determination means then determines whether an arcing estimation signal output by the extraction means is caused by arcing or not, and outputs an arcing detection signal if caused by arcing. Based on the arcing detection signal, a trip unit opens the contact. When the probability is high that the input waveform from the extraction means in a prescribed amount of time is a waveform caused by arcing, the arcing determination means increases a value in accordance with the probability, and when the probability is high that the waveform is a noise waveform other than arcing, the arcing determination means reduces the value in accordance with the probability. The increases and decreases are cumulated, and when the value meets or exceeds a prescribed amount, arcing is determined to be occurring.</p> |
