| 摘要 |
<P>PROBLEM TO BE SOLVED: To issue an alarm by determining existence of insulation deterioration when a frequency exceeding a threshold of an effective leakage current becomes high. <P>SOLUTION: When monitoring an insulation state of a power supply line in comparison with a threshold, by calculating an effective leakage current from a leakage current detected from a grounding line of the power supply line through a zero-phase current transformer, the number M of populations of the effective leakage current to be stored in a memory, the threshold A1 to the effective leakage current, and an upper limit ratio B of the threshold-exceeding number of the effective leakage currents exceeding the threshold A1 to the number M of populations are set beforehand, and the effective leakage current is calculated at a prescribed time interval, and stored in the memory successively. When the effective leakage currents to the number M of populations are stored in the memory, the threshold-exceeding number L of the effective leakage currents exceeding the threshold A1 is counted, and the ratio C of the threshold-exceeding number L to the number M of populations is determined, and when the ratio C is larger than the upper limit ratio B, an alarm signal for operating a prescribed informative means is outputted. <P>COPYRIGHT: (C)2010,JPO&INPIT |
