| 摘要 |
<p>PURPOSE:To enable a decision for existence of abnormality easily in a job site by receiving the output signal of a comparator circuit and outputting an alarm signal when a time width of the received output signal exceeds a specified threshold time. CONSTITUTION:An occurrence frequency of more than 50 times per sec, specified threshold of 2000 pc, and specified threshold time Td of 30 sec, are taken as decision references for a local discharge to be determined as abnormal. When the level of output signal 5S of a detecting rectifier 5 corresponding to the specified threshold of 2000 pc is expressed as Vm, then the signal 5S is peak-held and becomes an output signal 7S and converted to an output signal 10S with square wave of the comparator circuit 10 only in the sections A and B wherein the local discharge level is higher than Vm. Further, to detect the pulse width of square wave of the signal 10S in a determination circuit 11, e.g., the signal 10S is converted to an integrated value 11B by a built-in integration circuit, and this integrated value 11B is compared with a level V of integration value corresponding to the threshold time Td of 30 sec by a threshold time setting device 11A, then the decision is made whether the alarm signal 11S is outputted or not.</p> |
