| 摘要 |
<p>PURPOSE:To discriminate an ultrasonic wave generated inside a tank at corona discharge and an ultrasonic wave generated by the motion of metal particles by converting an ultrasonic wave signal into a pulse signal of fixed width, and judging whether or not there is some periodicity in the generation of pulses according to the result of measurement of the distribution of pulses generated within a reference time. CONSTITUTION:When partial discharge(corona) occurs at some point x on a conductor 2 located in a tank 1, ultrasonic wave is generated and transmitted while being reflected through the inside of the tank 1 and is converted into an electric signal when reaching the detection surface of an ultrasonic sensor 3. Ultrasonic wave generated by the motion of metal particles in the tank 1 is detected by the ultrasonic wave sensor 3 in the same way as mentioned above. A measuring circuit 11 for the distibution of time at which pulses are generated measures the distribution of time of pulse generation according to the output signal of a pulse generating circuit 10. A periodicity judging circuit 12 judges whether or not there is any periodicity in the generation of pulse. When there is some periodicity the ultrasonic wave is judged to be one generated at corona discharge, while when there is no periodicity the ultrasonic wave is judged to be one generated by the motion of the metal particles.</p> |
