| 摘要 |
PURPOSE:To normally monitor the analog input circuit of a digital relay while protecting a power system by synchronizing the oscillation at a test input signal oscillating section with the sampling clock of means for converting the analog amount of the analog input circuit into a digital amount. CONSTITUTION:When the output level H of a test input signal extraction filter 33 is within upper and lower limits, a level judging circuit 34 in a CPU 3 produces a normal signal G and notifies the fact on a display 6. When the output level H is lower than the lower limit or higher than the upper limit and that state endures for longer than a predetermined time, abnormality is notified on the display 6. According to the constitution, the analog input circuit 2 can be diagnosed with no influence on the essential relay function. |
